LO 3.1: The student is able to construct scientific explanations that use the structures and mechanisms of
DNA and RNA to support the claim that DNA and, in some cases, RNA are the primary sources of heritable
information.
SP 6.5: The student can evaluate alternative scientific explanations.
Explanation: The storage of information is crucial for the cell to continue on and preform properly. In order
for daughter cells to continue in their reproductive cycles and replications each cell has to receive genetic
information from the parent cells. Genes from the parents are passed on to the offspring from segments of
DNA and RNA which contain sequences of amino acids and proteins. The information needed is contained in
the DNA. However viruses can have RNA as well as DNA, which is able to store information needed to pass
on to the next generation. The unique structure of DNA allows it to form exact replications and pass them on
to the next generation in the form of genetic information. This is due to the nucleotide sequences that for
the DNA.
M.C. Question: Synthesis of a new DNA strand usually begins with?
A) A thymine dimer
B) DNA Primer
C) DNA Ligase
D) RNA Primer
Learning Log/FRQ-style Question: Describe the
process of DNA replication and how sexual
reproduction doesn’t produce identical offspring
from the parent. Explain why changes occur in the
DNA.
LO 3.2 The student is able to justify the selection of data from historical investigations that support
the claim that DNA is the source of heritable information.
SP 4.1 The student can justify the selection of the kind of data needed to answer a particular scientific
question.
Explanation: Many experiments were performed and analyzed on the path towards proving that DNA was the source of
heritable information, but two are particularly associated with the discovery. The first was performed by Frederick Griffith.
In his experiment, he used four mice to test for solutions. One contained live deadly bacteria, one live benign bacteria, one
dead deadly bacteria, and one both dead deadly bacteria and live benign bacteria. He injected one of these solutions into
four mice and observed the results. As expected, the one with the deadly bacteria died, and the ones with the benign
bacteria and the dead bacteria lived, but the one with both live benign bacteria and dead deadly bacteria died. He concluded
that some sort of genetic material exude from the dead bacteria and was incorporated by the live bacteria and caused it to
be deadly. The only question left was what part of the cell was the genetic material. This question was solved by the
Hershey/Chase experiment. They had found that bacteriophages consisted of only a protein shell and DNA, and that they
caused bacteria to incorporate some part of them and produce more, just like Griffith’s bacteria. They then designed an
experiment where two batched of bacteriophages were prepared. One was given a radioactive tracer that bonded with the
protein shells and one was given a radioactive tracer that bonded with the DNA. The batches were then separately
introduced to bacteria colonies and given time to insert their genetic material. The batches were then blended and
centrifuged to get the cell pieces (including genetic material) to the bottom of the tubes. The tube with the tracers in the
DNA showed it at the bottom of the tube meaning that DNA was what was incorporated into the bacteria cells and
therefore what carried genetic information.
M.C. Question: DNA’s use as heritable information relies on:
A)
B)
C)
D)
E)
Its nucleotide pairs
The phosphate backbone
Introns and exons
The codon order
Ribosomes
L.O 3.2
Learning Log/FRQ style Question: DNA is often transferred between bacterial cells. Name three ways in
which DNA can be transferred between two cells and explain how each works as a transfer of genetic
information.
LO 3.3: The student is able to describe representations and models that illustrate how genetic information is copied
for transmission between generations.
SP 1.2: The student can describe representations and models of natural or man-made
phenomena and systems in the domain.
Explanation: The cell cycle and DNA replication are responsible for passing on and copying genetic information between
generations. During interphase of meiosis, the cell grows and copies its chromosomes containing genetic material. The first
step in DNA replication is the unwinding of the double helix structure by the enzyme helicase. Single strand binding protein
binds to and stabilizes the single stranded DNA. DNA polymerase III synthesizes the leading strand in the 5’ to 3’ direction
while primase begins synthesis of the RNA primer for the Okazaki fragments. DNA polymerase III dissociates when it
reaches the RNA primer on each fragment, then moves to the replication fork and adds DNA nucleotides to the 3’ end. DNA
polymerase I removes the primer from the 5’ end and DNA ligase bonds the Okazaki fragments together. After interphase,
meiosis I begins with the crossing over of chromosomes (DNA molecules) to form tetrads. During metaphase I, the tetrads
line up in the middle of the cell and in anaphase I, the homologous chromosomes move toward opposite poles. Once there are
two haploid cells, the chromosomes line up in the middle of the cell again and as the cell grows, the sister chromatids are
separated- leaving four haploid daughter cells with genetic information that is not identical.
M.C. Question: Suppose there is a disorder which prevents
synapsis from taking place during meiosis. This would cause all
of the following EXCEPT
A) Four haploid cells containing identical genetic
information to be produced.
B) A decrease in genetic variation due to the inability
of a cleavage furrow to form.
C) The inability of chiasmata to hold the
homologues together in meiosis I.
D) Genetically identical sister chromatids of each
chromosomes in meiosis II.
Learning Log/FRQ- Style Question: Describe the role of the following in DNA replication: Helicase, Primase, DNA Ligase,
DNA polymerase. Explain what happens to the chromosomes during the three stages of meiosis. Explain how crossing over
causes genetic variation.
LO 3.4: The student is able to describe representations and models illustrating how genetic information is translated into polypeptides.
SP 1.2: The student can describe representations and models of natural or man-made phenomena and systems in the domain.
Explanation: Once transcription has occurred and the gene strand has been processed into mRNA, it leaves the nucleus and heads to
the ribosome. At first the ribosome is made up of two parts- the small and large subunits- and they bind together as the mRNA binds
to the small subunit, and the start codon (AUG) uses GTP to bind the large subunit. The large subunit has three main sights: E sight
(where the tRNA Exits), P site (Peptidyl- tRNA binding sight), and the A site (Aminoacyl- tRNA binding site). The tRNA anti-codon
matches with the complementary codon in the A site via the hydrolysis of GTP. An rRNA molecule of the large subunit catalyzes the
formation of a peptide bond between the amino acid in the A site and the carboxyl end of the growing polypeptide in the P site (this
attaches the polypeptide to the tRNA in the A site). The ribosome translocates the tRNA (by the use of more GTP) from the A site to P
sites and the empty tRNA than was in the P site is moved to the E site and ejected from the ribosome to be recycled. These steps can
be summarized as: codon recognition (anticodon to codon in the A site), peptide bond formation (from site P to A), and Translocation
(the movement from site A to P to E). Once when a ribosome reaches a stop codon on mRNA, the A site accepts a protein called a
release factor instead of tRNA. The release factor hydrolyses the bond between the tRNA in the
P site and the last amino acid of the polypeptide chain. The polypeptide is they freed from the
ribosome. The two ribosomal subunits and the other components of the assembly dissociate
leaving the ribosome ready for another round of translation.
M.C. Question: Suppose a protein were to be built incorrectly, thus creating a
nonfunctional polypeptide. All of the following could be a cause EXCEPT:
A) There was an error as the GTP hydrolyzed anticodon and codon
mismatched the wrong tRNA thus bonding the incorrect amino acid.
B) The mRNA strand had an error in the nucleotide sequence after
transcription and RNA processing.
C) In the P site, the ATP failed in binding the amino acid from the incoming
tRNA in the A site.
D) The mRNA strand had an error which caused the stop codon to be out of
place, causing the protein to be longer than required.
FRQ: Draw and label a ribosome and its respective parts during
translation. Describe the function of each element in the gene-topolypeptide process.
LO 3.5: The student can justify the claim that humans can manipulate heritable information by identifying at least
two commonly used technologies.
SP 6.4: The Student can make claims and predictions about natural phenomena based on scientific theories and
models.
Explanation: Humans can manipulate heritable information in bacterium (gene cloning) with plasmids by insertion of foreign
DNA into the plasmid. Then the host bacterium forms colonies of cells with the new gene of interest. Then these bacterium
can be inserted into other organisms who need that gene. Such as the gene for pest resistance inserted into plants. Also Gene
Therapy, the alteration of an afflicted individual’s genes, holds great potential for treating disorders traceable to a single
defective gene. Gene Therapy can use a retrovirus as a vector that inserts a DNA transcript of its RNA genome into the
chromosomal DNA of its host cell. If the foreign gene carried by the retroviral vector is expressed, the cell and its
descendants will possess the gene product, and the patient will be cured. So humans can base the idea of DNA and RNA as
the code for producing how organisms functions so they can survive. If the organism does not function normally, or can be
used to do other tasks we can alter its genome in a way that it can function better.
M.C. Question:
Which of the following is not true about restriction enzymes?
A. They protect bacterial cells against the introduction of DNA from other organisms
by cutting up foreign DNA
B. They create a site for a eukaryotic gene to be inserted into a bacterial plasmid
C. They bind bacterial DNA fragments together
D. They cut the sugar phosphate backbone of bacterial DNA to create sticky ends
Learning Log/ FRQ-style Question: How could someone test to know if the specific
gene is cloned correctly into the plasmid? Also, how could someone prepare large
quantities of a particular gene or other DNA sequence using PCR and how would this
be useful?
LO 3.6 The student can predict how a change in a specific DNA or RNA sequence can result in
changes in gene expression.
SP 6.4 The student can make claims and predictions about natural phenomena based on
scientific theories and models.
Explanation: In both DNA and RNA, there are sequences of 3 nucleotides on a strand called
codons. Each codon codes for a specific gene that will later be expressed when the genes are
coded for amino acids to make proteins. If a change in a sequence occurred, for example, if one
nucleotide was taken out in a point mutation, this would result in a frame shift. When one
nucleotide is taken out, the sequences on either side simply slide over. This, however, ends up
changing every single codon on one side. Whatever protein the codons made before the mutation
will have changed. Now during translation, the sequence of 3 nucleotides in each codon will be
different. Now new proteins will be made and, therefore, express the change in the sequence of
the gene.
M. C. Which of the following would cause the most change in gene
expression?
a. A codon deletion in the middle of a coding sequence.
b. A base pair substitution at the beginning of a coding sequence.
c. A deletion of a single nucleotide in a coding sequence.
d. An insertion of a codon at the beginning of a sequence.
Learning Log/FRQ-style Question:
Sickle cell anemia is the result of a point mutation in the codon for
glutamine in a DNA sequence. Describe the process of the point
mutation causing the disease and how it leads to the expression
of the disease.
LO 3.7 The student can make predictions about natural phenomena occurring during the cell cycle.
SP 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models.
Explanation: The cell cycle is a complex set of stages that is highly regulated with checkpoints, which determine the
ultimate fate of the cell. Interphase consists of three phases: growth, synthesis of DNA, preparation for mitosis. Internal and
external signals provide stop-and-go signs at the checkpoints. Mitosis alternates with interphase in the cell cycle. Mitosis
passes a complete genome from the parent cell to daughter cells and occurs after DNA replication. Mitosis followed by
cytokinesis, produces two genetically identical daughter cells. Mitosis plays a role in growth, repair, and asexual
reproduction. Meiosis, a reduction division, followed by fertilization ensures genetic diversity in sexually reproducing
organisms. Meiosis ensures that each gamete receives one complete haploid (1n) set of chromosomes. During meiosis,
homologous chromosomes are paired, with one homologue originating from the maternal parent and the other from the
paternal parent. Orientation of the chromosome pairs is random with respect to the cell poles. Separation of the
homologous chromosomes ensures that each gamete receives a haploid (1n) set of chromosomes composed of both
maternal and paternal chromosomes. During meiosis, homologous chromatids exchange genetic material via a process
called “crossing over,” which increases genetic variation in the resultant gametes. Fertilization involves the fusion of two
gametes, increases genetic variation in populations by providing for new combinations of genetic information in the zygote,
and restores the diploid number of chromosomes.
M.C. Question: Increases in the enzymatic activity of some protein kinases important for the regulation of the cell cycle are
due to
a) Kinase synthesis by ribosomes
b) Activation of inactive kinases by binding to cyclins
c) Conversion of inactive cyclins to active kinases by means of phosphorylation
d) Cleavage of the inactive kinase molecules by cytoplasmic proteases
A decline in external growth factors to a concentration below the inhibitory threshold
FRQ: The cell cycle is fundamental to the reproduction of eukaryotic cells. Explain
the role of THREE of the following in mitosis or cytokinesis.
•
Kinetochores
•
Microtubules
•
Motor proteins
•
Actin filaments
L.O. 3.8 The student can describe the events that occur in the cell cycle.
S.P. 1.2 The student can describe representations and models of natural or man-made
phenomena and systems in the domain.
The cell cycle is a series of events that allows an organism to grow through the production of more cells. The
cycle is made of four stages, the G1 phase, a “gap” period of cell growth, the S phase of DNA replication, the
G2 phase, a second “gap” period of growth and preparation for mitosis, and finally the mitotic (M) phase.
Although the M phase is usually the shortest phase, it is the most critical. During the M phase, chromosomes
condense (prophase), line up at the center of the cell (metaphase), and are pulled apart by the mitotic
spindle fibers (anaphase). Two daughter nuclei then form (telophase) and the cells undergo cytokinesis. The
two new daughter cells then enter the G1 phase. The cell cycle is regulated by three main checkpoints in the
G1, G2, and M phases. These checkpoints are somewhat of a “stop” signal that halts the cell cycle until they
are overridden by “go ahead” signals. Examples of such signals are maturation-promoting factors (MPFs),
complexes of cyclins and Cdks that allow the cell to enter the M phase.
M.C. Question: What could be an effect on a
cell if the binding of cyclin and CDK was
inhibited?
a. The cell would enter the G0 phase
b. The cell would be unable to enter the M
phase and would be unable to divide.
c. Following division, Cdk would be unable to
be recycled.
d. Apoptosis would occur immediately.
c. Both A and B
FRQ/LL Question:
The interactions between Cdk
molecules and cyclins are an
Important aspect of the cell cycle.
Discuss the interactions between these two molecules
and their effects on the regulation of the cell cycle.
Include an explanation of the effects on the cell if cyclins
are produced in excess.
LO 3.9: The student is able to construct an explanation, using visual representations or narratives, as to how DNA in
chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization.
SP 6.2: The student can construct explanations of phenomena based on evidence produced through scientific practices.
Explanation: Mitosis produces 2 daughter cells that are identical to the parent cell, and is prevalent in asexual reproduction. Mitosis also
allows organisms to grow and develop and repair damaged cells. Meiosis produces gametes (sperm and egg) that have half the number of
chromosomes as the parent cell; these gametes enable an organism to reproduce sexually.
Mitosis: Prior to mitosis, a cell grows and develops during interphase, during which a cell spends approximately 90% of its life cycle.
During interphase the chromosomes are not yet visible, and the nuclear envelope is still present. At the end of interphase, each
chromosome makes an identical copy of itself. The cell then enters the mitotic phase. During prophase, the chromosomes condense and
centromeres begin to migrate to opposite sides of the cell. In metaphase, chromosomes line up down the middle of the cell and spindle
fibers attach themselves to the chromosomes. During anaphase, the sister chromatids split apart before moving to opposite sides of the
cell during telophase. Cytokinesis Is the last step, by which the cell is split down the middle forming 2 identical daughter cells, identical to
the original parent cell.
Meiosis: Meiosis only occurs in the testes/ovaries, and it produces haploid gametes that unite to form a diploid zygote via fertilization.
Meiosis, like mitosis, undergoes the same phases, only, meiosis undergoes each twice. Prior to meiosis 1, the cells paternal and maternal
chromosomes are copied; these 4 resulting chromosomes line up during prophase 1 of meiosis 1 and are known as a tetrad. During meiosis
1 the tetrad splits and the germ line cell results in 2 different cells. Crossing over will usually occur during prophase 1; during this, DNA
between maternal and paternal chromosomes gets swapped, which causes genetic variation amongst resulting gametes. After meiosis 1 is
complete, the 2 resulting cells reproduce again via meiosis II, resulting in 4 overall gametes. Each gamete is different from each other due to
crossing over and the law of independent assortment, which says that it is totally random as to how and in what order the tetrads line up.
The resulting 4 gametes are then used to fertilize a gamete of the opposite sex to produce a zygote. All organisms undergo some form of
meiosis except bacteria which only reproduce asexually.
MC: Which of the following would
result after meiosis II of a germ line
cell with 10 pairs of homologous
chromosomes?
A.) 4 Gametes, each with 10 pairs of
homologous chromosomes.
B.) 4 identical copies of the original
germ line cell.
C.) 4 gametes, each with 10
chromosomes, 1 from each
homologous pair.
D.) 2 gametes, each with 10 sister
chromatids.
FRQ:
Describe 2 ways by which a
newly fertilized zygote will
have genetic variability. This
offspring will not be
genetically identical to any
other offspring of the same
parents-why?
LO 3.10: The student is able to represent the connection between meiosis and increased genetic diversity
necessary for evolution
SP 7.1: the student can connect phenomena and models across spatial and temporal scales.
Explanation: Meiosis, along with fertilization that follows provides an abundance of phenotype possibilities
that increases genetic diversity. In all cases of meiosis a parent cell divides into four gametes that each
contain half the genetic material as the parent. In Meiosis 1 the homologous chromosomes exchange
genetic material in a process called crossing over so the daughter cells each have a mix of the parents genes.
When Meiosis 2 occurs these recombined chromosomes split into their respective sister chromatids creating
a new genetically diverse gamete. Since crossing over happens at random segments of the DNA, the gametes
formed are almost always different than the millions of others produced.
M.C. Question: In what way does the process of Meiosis contribute to genetic diversity?
A) It splits the sister chromatids unevenly, allowing for some gametes to have more genetic material than
others
B) Homologous chromosomes exchange DNA in a process called crossing over in Meiosis 1
C) Gametes quickly exchange chromatids before they split apart in meiosis 2
D) Gametes form tight junctions between each other and exchange sections of chromosomes
Learning Log/ FRQ-style Question:
A)Explain how the Duplication, rearrangement, and reduction
of genetic material during meiosis contributes to genetic
Diversity within an organism.
B)Give an example of how an error in meiosis can lead to
Damaging traits in an organisim.
LO 3.11 The student is able to evaluate evidence provided by data sets to support the claim that heritable information is
passed from one generation to another generation trough mitosis, meiosis, followed by fertilization
SP 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question.
Explanation Meiosis and mitosis are two very similar processes, which both involve replication, duplication, and division of
certain cells in the body. Meiosis differs from mitosis in the way that this process divides gamete cells, sperm cells in males, and
egg cells in females. Mitosis is a process that occurs in all body cells, except for gamete cells which are used for sexual
reproduction purposes. Meiosis is the main way that genes can be passed from genetic parents down to their offspring. When
the two gametes of each sex come together, or fertilize, the genes are mixed and are expressed in different ways in their
offspring. Many genes are expressed either dominantly or recessively in the offspring, but this depends on the parents genes
that are passed on. An example would be if you have received a dominant trait for widows peak from both parents, then you
will receive that trait. This principle can also apply to someone who receives a dominant and recessive genefor this one trait
from each of the parents, but if given both recessive genes then trait will not be expressed.
M.C. Question Based on what you know about mitosis and meiosis, which of the following is false concerning these two
processes?
A)
Meiosis is the process of dividing a nucleus of the cell into two cells who each have half the number of chromosomes as
the 1st phase.
B)
Mitosis is a way for the body to repair tissues and fibers.
C)
Meiosis is a process where cells are split two separate times, with chances of chromosomal mixing.
D)
Mitosis is an asexual, six step process that replicates cell information to make a cell of equal standards.
FRQ-style Question: If you have chromosomal deficiencies in your cells, is
that a problem with the meiosis or mitosis process? Why? In what ways
could a negative altercation of mitosis become worse than a negative
altercation of meiosis?
LO 3.12 The student is able to construct a representation that connects the process of meiosis to the
passage of traits from parent to offspring.
SP 1.1 The student can create representations and models of natural or man-made
phenomena and systems in the domain.
Explanation: Meiosis is the process by which gametes, or sex cells are produced from diploid parent cells to create haploid
cells in order to facilitate the fusion with a haploid of the opposite sex and produce genetically different offspring. During
interphase, homologous pairs of chromosomes line up in the cell, these chromosomes represent DNA that was received from
the parent organism. Crossing over can occur at the chiasmata of homologous nonsister chromosomes during prophase I.
This crossing over allows for increased genetic variability as genes from different chromosomes are able to be exchanged.
After crossing over the homologous chromosomes are pulled to opposite poles by microtubules attached at the centromere.
After telophase I and cytokinesis, the two diploid cells then have the sister chromosomes, which contain the alleles that
determine genetic and phenotypic traits of the offspring, separated and the cells undergo cytokinesis once more to create four
haploid cells that are genetically different from the parent. These gametes have only half of the alleles for each parental trait,
increasing the genetic possibilities for the offspring.
M.C. Question: Which of the following statements is true regarding meiosis?
A) Meiosis involves the duplication and separation of genetically identical cells.
B) Meiosis allows for increased genetic diversity by producing four gametes that
have differing genetic material from the parent cell, thus enabling the offspring to
differ from the two parent organisms.
C) Epidemics can move through a population with greater ease if the species’
reproductive system uses meiosis due to the resulting decrease in genetic
variability.
D) Meiosis is a more efficient way to reproduce as it requires less steps and energy
than simple mitosis.
Free Response Question: Suppose an organism has an unknown adaption due to the allele AaBb. Create a labeled
diagram to trace the passage of the allele from the parent to its offspring. Why is the use of meiosis more beneficial to the
species as a whole? What is one potential problem that the process of meiosis could cause for the offspring?
LO 3.13 The student is able to pose questions about ethical, social or
medical issues surrounding human genetic disorders.
The student can pose scientific questions.
Explanation: There are many different genetic disorders that can
affect the human body. Most of them can affect that person for the
rest of their lives. One of the disorders is called Turner’s Syndrome
it is a mutation in the genome that stops a protein from forming
correctly thus not removing waste from the nerve cells.
MC Question
If a patient is suspected mentally handicapped.
What would be the most likely method for Turner’s
syndrome testing.
A) test for a gene for coding for an enzyme that
breaks down waste in the brain.
B) A extraction of a sample cell to test for waste.
C) Use X Rays to look at the entire body
D) Remove the affected cells of the patient
FRQ:
Describe the four different genetic disorders from the
list and explain the consequences of having the disorder
in molecular level as well as in life in general.
Tourette Syndrome , Colorblindness, Huntington's
disease, sickle-cell anemia.
In this picture the doctor is extracting the
amniotic fluid from the womb, the doctor
could then test the fluid for various genetic
disorders. The parents then could decide
weather to keep the baby or not. This raises
many ethical issues
LO 3.14: The student is able to apply mathematical routines to determine
Mendelian patterns of inheritance provided by data sets.
SP 2.2: The student can apply mathematical routines to quantities that describe natural
phenomena.
Explanation: You can use rules of probability to determine the chances of a certain coupling to
reproduce an offspring with a certain genotype. For example, if you cross a male with the genotype
AaBb with a heterozygous female with the same genotype and you want to figure out the probability
of them producing an offspring with a genotype AABB, you would multiply ½ x ½ because there is a ½
chance of producing AA from AaxAA and a ½ chance of producing BB from BbxBB.
M.C. Question: If you do the cross AABBxAaBb, what are the chances of an offspring with the genotype
AaBb being produced?
A) 1/2
B) 1/4
C) 1/64
D) 1/8
E) 1/16
FRQ: Describe the three types of genetic dominance and provide an
example of each, making sure to explain the effects on the
phenotype of an offspring.
LO 3.15 :The student is able to explain deviations from Mendel’s model of the inheritance of traits.
SP 6.5: The student can evaluate alternative scientific explanations.
Explanation: The inheritance pattern of many traits can be explained by simple Mendelian genetics. Many traits are
products of multiple genes or various physiological processes that don’t occur naturally. Traits that don’t follow Mendel’s
laws can be identified when resulting phenotypic ratios differ statistically from predicted ratios and results. Some traits are
sex linked and determined by genes on the sex chromosome (X Chromosome in humans.) In mammals and flies, females
are XX and males are XY, the Y Chromosome is small and carries few genes, therefore X-linked recessive traits are always
expressed in males. Some traits are sex limited and expression depends on specific sex; examples being milk production in
females and pattern baldness in males. Some traits result from nonnuclear inheritance such as with chloroplasts and
mitochondria which are randomly assorted to gametes and daughter cells; thus, traits determined by chloroplasts and
mitochondrial DNA don’t follow Mendelian rules. In animals, mitochondrial DNA is transmitted by the egg instead of the
sperm therefore all mitochondrial-determined traits are inherited from the mother.
M.C. Question: Albinism is a lack of pigmentation in humans caused by
an autosomal recessive gene. What is the probability that two parents
with normal pigment have 3 children in a row that all suffer from
Albinism?
A) 1/8
B) 1/4
C) 1/16
D) 1/64
Learning Log/FRQ-Style Question:
State the conclusions reached by Mendel in his work on
the inheritance of characteristics. Explain how each of the
following deviates from these conclusions:
A. Autosomal linkage
B. Sex-linked (X-linked) inheritance
C. Polygenic (multiple-gene) inheritance
•
LO 3.16: The student is able to explain how the inheritance patterns of many traits cannot be accounted for by Mendelian genetics.
SP 6.3: The student can articulate the reasons that scientific explanations and theories are refined or replaced
Explanation: The patterns in which traits are inherited, cannot all be accounted for by Mendelian genetics. Mendel has set laws, but not all
traits fall onto the path these lead. Some observed phenotypic ratios can statistically differ from the predicted outcomes. Along with this,
some genes can be passed down on sex chromosomes. An example of a sex-chromosome-linked trait would be colorblindness. This is a
recessive allele found on the x-chromosome, affecting males more frequently. Mendelian genetics do not account for sex linked traits,
therefor ot accounting for the colorblind allele. Another example of sex linked traits, would be milk production and pattern baldness.
Mendel stated that different traits are inherited independently of each other, so there is no relation, but this is only true for traits that are
not linked to each other. In some cases, with the use of Mendel’s laws, incomplete dominance would occur. Incomplete dominance is
when the dominant allele does not seem as apparent. For example, a red flower and a white flower are crossed, and a pink flower is the
product, the pink flower is a mixture showing incomplete dominance. Another circumstance like incomplete dominance is co-dominance.
In this scenario, a red flower and white flower would come out with a flower that is speckled both red and white. Now, Mendel’s laws of
genetics have been modified into what we call “modern genetics” where most of his ideas are still relevant.
Multiple Choice:
Colorblindness is sex-linked and recessive in humans. A woman with normal vision
but whose father was color blind marries a man with normal vision whose father was
also color blind. What type of allele can be expected of their four offspring?
A) both sons being colorblind, both daughters carriers
B) one daughter and one son colorblind, and one daughter and one son carriers
C) one son normal, one daughter normal, one son colorblind, and one daughter a
carrier
D) one son colorblind, one son carrier, and both daughter carriers
Free Response Question:
Draw and label a pedigree showing the passage of the sex-linked allele of
colorblindness. Make sure to describe all factors contributing to the outcome
and why it happened.
LO 3.17: The student is able to describe representations of an appropriate example of inheritance patterns that cannot be explained by Mendel’s
model of the inheritance of traits.
SP 1.2: The student can describe representations and models of natural or man-made phenomena and systems in the domain.
Explanation: Mendel’s model of inheritance is based on the idea that each parent contributes one of two possible alleles for a trait. If the
genotype of the two parents is known, the distribution of phenotypes expected for the population of offspring can be determined. The unusual
inheritance patterns are incomplete dominance, codominance, multiple alleles, epistasis, pleiotropic, polygenic, and linked genes. Incomplete
dominance is the idea that two phenotypes are blended rather than showing two different possibilities. Before Mendel, it was believed that
organisms underwent incomplete dominance and therefore the blended parental traits could not be separated in later generations.
Codominance is when both alleles are expressed at the same time. Multiple alleles is when there are more than two alleles. Blood type is
controlled by three alleles: A, B and O. AB blood type is an example of codominance. Epistasis is when a gene at one location affects or alters the
expression of a gene at another location. Pleiotropy is the ability of a single gene to exert influence on several characteristics, meaning that they
have multiple effects on the phenotype of the species (many arise from genes whose products are involved in signaling and regulation
pathways). Polygenic inheritance is when a phenotype is determined by two or more genes. Linked genes are genes that stay together during
assortment and move as a group. Sex linked traits (X-linked) are carried on sex chromosomes, and if the allele is defective on the X chromosome
it will show up on males much more than females because women have Barr bodies.
M.C. Question:
Which of the following statements concerning sex-linked traits is true?
a. A female offspring's expression of a sex-linked trait is determined by the genotype of her mother.
b. A female offspring's expression of a sex-linked trait is determined by the genotype of her father.
c. Male and female offspring have the same probability for the expression of a sex-linked trait.
d. A male offspring’s expression of a sex-linked trait is determined by the father.
e. B and D
Learning Log/FRQ-style question:
Look at the picture below and explain the phenotypic ratio of the first and second generations of offspring. Explain the inheritance principle that
allows pink flowers to be made. Use punnett squares in your explanation.
LO 3.18: The student is able to describe the connection between the regulation of gene expression and
observed differences between different kinds of organisms.
SP 7.1: The student can connect phenomena and models across spatial and temporal scales.
Explanation: Gene regulation accounts for some of the phenotypic differences between organisms with
similar genes. Gene expression is controlled by an inducer and inhibited by a repressor. Regulatory proteins
inhibit gene expression by binding to DNA and blocking transcription. They stimulate gene expression by
binding to DNA and stimulating transcription or binding to repressors to inactivate repressor functions. The
combination of transcription factors binding to regulatory regions determine how much of the gene product
will be produced.
Promoter
Stages of Transcription:
Transcription unit
M.C. Question: In prokaryotes, gene
expression involves:
A) regulatory genes
B) transcription factors
C) Regulatory elements
D)Polyribosomes
5
3
3
5
Start point DNA
Initiation. After RNA polymerase binds to
RNA polymerase
1 the promoter, the DNA strands unwind, and
the polymerase initiates RNA synthesis at the
start point on the template strand.
5
3
Learning Log/FRQ-style Question:
Organisms share a high quantity of DNA.
Give phenotypic evidence of different
organisms sharing similar DNA.
Template strand of
DNA
2 Elongation. The polymerase moves downstream, unwinding the
transcript
DNA and elongating the RNA transcript 5  3 . In the wake of
Rewound
transcription, the DNA strands re-form a double helix.
RNA
3
Unwound
DNA
5
3
3
5
RNA
3
5
5
RNA
transcript
3 Termination. Eventually, the RNA
transcript is released, and the
polymerase detaches from the DNA.
5
3
3
5
3
5
Completed RNA
transcript
LO 3.19: The student is able to describe the connection between the regulation of gene expression and
observed differences between individuals in a population.
SP 7.1: The student can connect phenomena and models across spatial and temporal scales.
Explanation: The regulation of genes in a population effects the expression of genes and the overall
appearance of the population. The differences in the expression of certain genes changes physical
appearances caused by either the activation or repression of the gene. Regulatory genes can be
influenced by environmental factors that could, for example, effect wing shape in fruit flies. The
repressors are activated to stop processes like the growth of harmful cells to keep the body healthy.
Regulatory genes work by binding or unbinding to a gene to stimulate or repress the transcription of it.
MC Question: What would not be an instance when gene
regulation would be used?
A. Stopping the growth of a tumor
B. Genetic changes in the body color of a fruit fly
C. The shift in a population toward larger animals
D. The building of certain proteins used in RNA
FRQ Question:
Regulatory genes regulate protein activity.
Discuss TWO specific mechanisms of
protein regulation in eukaryotic cells.
LO 3.20 The student is able to explain how the regulation of gene expression is essential for the process and
structures that support efficient cell function. [see SP 6.2]
SP 6.2 The student can construct explanations of phenomena based on evidence produced through scientific
practices.
Explanation:
Gene expression is necessary for cells to function properly; it allows cells to differentiate into different organs.
The same genes can be expressed in an array of ways from the same DNA.
Multiple Choice: Why may a set of identical twins each have a feature that slightly appears to differ from his/her
sibling?
A )They aren’t really identical.
B) There has been a mutation of genes in one of the twins.
C) The code for that particular gene may be expressed in a variety of ways depending on how the body
translates/reads it.
D) There has been a deletion of insertion.
E) Both a and d are correct.
FRQ:
Gene expression regulates efficient cell function in many ways. Explain how the following contributes to this:
a) cell differentiation
b) role of proteins
c) DNA methylation
LO 3.21 The student can use representations to describe how gene regulation influences cell products and function.
SP 1.4 Gene regulation accounts for some of the phenotypic differences between organisms with similar genes.
Explanation: Regulation of gene expression refers to the control of the amount and timing of appearance of the functional
product of a gene. Control of expression is vital to allow a cell to produce the gene products it needs when it needs them; in
turn this gives cells the flexibility to adapt to a variable environment, external signals, damage to the cell, etc. Some simple
examples of where gene expression is important are: control of Insulin expression so it gives a signal for blood glucose
regulation X chromosome inactivation in female mammals to prevent an "overdose" of the genes it contains. Cyclin
expression levels control progression through the eukaryotic cell cycle, more generally gene regulation gives the cell control
over all structure and function, and is the basis for cellular differentiation, morphogenesis and the versatility and
adaptability of any organism. Any step of gene expression may be modulated, from the DNA- RNA transcription step to posttranslational modification of a protein. The stability of the final gene product, whether it is RNA or protein, also contributes
to the expression level of the gene - an unstable product results in a low expression level. In general gene expression is
regulated through changes in the number and type of interactions between molecules that collectively influence
transcription of DNA and translation of RNA.
Which of the following statements correctly describes promoters in E.
coli?
A) A promoter may be present on either side of a gene or in the middle
of it. B)Every promoter has a different sequence, with little or no
resemblance to other promoters. C) Many promoters are similar and
resemble a consensus sequence, which has the highest affinity
for RNA polymerase holoenzyme. D) Promoters are not essential for
gene transcription, but can increase its rate by two- to three-fold.
Describe and contrast positive regulation and negative regulation of gene
expression.
LO 3.22: The student is able to explain how signal pathways mediate gene expression, including how this process can
affect protein production.
SP 6.2: The student can construct explanations of phenomena based on evidence produced through scientific practices.
Explanation: Signals can be transmitted between cells through paracrine, local signaling, or endocrine, long distance
signaling, pathways using signal molecules called ligands. These ligands bind to receptor proteins either on the surface of
the plasma membrane, or inside the cell. Steroid hormones are lipids, so they are hydrophobic and can travel through the
plasma membrane, so they attach to receptors inside the cell, creating a hormone-receptor complex, which travels to the
nucleus and activates certain genes to be transcripted into RNA and then translated into specific proteins. Protein ligands
are hydrophilic and cannot pass through the plasma membrane, so they bind to receptors in the extra-cellular-matrix and
can allow certain genes to be transcripted and/or cause other responses within the cell. When a ligand binds to a TyrosineKinase receptor, the two separate halves form a dimer, which phosphorylates using ATP and initiates relay proteins. Once a
ligand binds to a G-Protein-Linked receptor, the receptor phosphorylates a G-protein using GTP. The G-protein then
phosphorylates an enzyme. Ligand gated ion channels either open when the
ligand attaches to let ions pass freely between the cytosol and extracellular fluid
or close when the ligand attaches to cease the flow of ions.
M.C. Question: Explain why a steroid hormone binds to receptors inside the cell
when protein ligands bind to receptors in the extra-cellular matrix.
a)
Steroid hormones mediate gene expression, so they have to bind to their
receptors while they are in the nucleus.
b)
Protein ligands only bind to ligand-gated-ion channels, which must be
embedded in the plasma membrane.
c)
Steroid hormones can travel through protein channels across the plasma
membrane to enter the cell and protein ligands cannot.
d)
Steroid hormones are hydrophobic, so can travel through the plasma
membrane and protein ligands are hydrophilic, so they cannot.
Learning Log/FRQ-style Question: Explain how a signal can be transmitted from
one cell to another cell resulting in a physical response by the cell and the
alteration of gene expression in the receptor cell. Include in your explanation
two types of receptor proteins and describe how they function.
LO 3.23: The student can use representations to describe mechanisms of the regulation of gene expression
SP 1.4: The student can use representations and models to analyze situations or solve problems
qualitatively and quantitatively
Explanation: In cells, gene regulation is necessary to regulate the production of gene products. In DNA,
demethylation occurs to prevent transcription from occurring. Acetylation unwinds DNA for simple
transcription to take place. In RNA, small interfering RNA or siRNA, targets and degrades mRNA. In
DNA, the promoter reigon increases RNA polymerase binding while the Enhancer increases
transcription. DNA packaging tightens or loosens the chromatin to inhibit or promote transcription.
M.C. Question: Which of the following is not involved in gene
regulation?
a) RNA processing
b) Apoptosis
c) Degredation of mRNA
d) Cleavage and Transport
FRQ: Cancer is caused by mutations and errors in regulation.
Describe the factors necessary for cancerous cells to develop.
LO 3.24: The student is able to predict how a change in genotype, when expressed as a phenotype,
provides a variation that can be subject to natural selection.
SP 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate
in and/or across enduring understandings and/or big ideas.
Explanation: Mutations, random changes in DNA sequences, are
the most common cause of genetic variation. When DNA
sequences (genotypes) are altered, the phenotype of an
organism may be altered as well due to changes in protein
production, and depending on the environment and natural
selection, such altered phenotypes may be beneficial to
organisms (as genetic variation often is). In a population of
bacteria, for example, a few individual bacteria may develop (by
mutation) antibiotic-resistance genes. If this happens, then the
mutated bacteria will survive and produce offspring that is
completely resistant to the antibiotic. In this way, small changes
in the genotypes of just a few individuals can lead to the
evolution of an entire population.
students.cis.uab.edu
M.C. Question: Which of the following is true?
A) Nondisjunction of chromosomes is always fatal to an organism.
B) A chromosomal point mutation generally causes more drastic
changes in genotype than a chromosomal deletion.
C) Females with trisomy X are phenotypically indistinguishable from
normal XX females.
D) Evolutionary forces always select against mutated organisms.
Learning Log/FRQ-style Question: The antibiotic-resistance
gene developed by the bacteria described above is one
example of a beneficial mutation. Provide another. Also,
describe some of the mechanisms by which mutations are
prevented during or after DNA replication.
evolution.berkeley.edu
LO 3.25: The student can create a visual representation to illustrate how changes in a DNA nucleotide sequence can result in a change in the polypeptide produced.
SP1.1: The student can create representations and models of natural or man-made phenomena and systems in the domain.
Explanation: Nucleotides are known as the basic building block for the construction of polypeptide chains, most commonly known as
proteins. They consist of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. There are four nitrogenous
bases included in DNA: adenine, thymine, cytosine, and guanine. In RNA the thymine is replaced with uracil. Nucleotides are read in intervals
of three and represent a codon. If a single nucleic acid is changed, then the specified codon would also be different. Codons, in turn, are
translated into amino acids that form peptide chains. The most common type of mutation is a point mutation. In point mutations, a single
base-pair is changed. There are 3 kinds of single base-pair mutations: base-pair substitutions, insertions, and deletions. A base-pair
substitution is the replacement of one nucleotide and its partner with another pair of nucleotides. It may lead to silent, missense, or
nonsense mutations. If no change is made to the amino acid sequence, then the mutation is silent. Most substitution mutations are missense
mutations; the altered codon still codes for an amino acid and thus makes sense, although not necessarily the right sense. If a change in the
nucleotide results in the premature ending of the polypeptide chain, it is known as a nonsense mutation. Insertions and deletions are
additions or losses of nucleotide pairs in a gene. Such a change can cause the reading frame, codons, to change. Such a mutation, called a
frameshift mutation, will occur whenever the number of nucleotides inserted or deleted is not a multiple of three. The following codons will
then be incorrect. In turn, the entire polypeptide chain after that point will also be incorrect.
M.C. Question: Which of the following changes to the DNA sequence, AGC-GCT-TAA-CGC-AGT-ATTCGA-GCT, would have the greatest effect when being translated into amino acids?
a. The guanine in the first triplet is replaced with a thymine nitrogenous base.
b. The guanine in the fourth triplet is replaced with a cytosine nitrogenous base.
c. The guanine of the eighth triplet is replaced with a adenine nitrogenous base.
d. The guanine of the seventh triplet is replaced with a thymine nitrogenous base.
Learning Log/FRQ-style Question: Information flow can be altered by
mutation. Describe three different types of mutations and their effect on
protein synthesis.
LO 3.26: The student is able to explain the connection between genetic variations in organisms and phenotypic variations in
populations.
SP 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring
understandings and/or big ideas.
Explanation: Random changes in a DNA sequence, or mutations, create genetic variations that in turn alter the consequent
phenotypes in a positive, negative, or neutral manner depending on external environmental factors. Such a change can be
caused by errors in DNA replication or repair mechanisms. For example, a deletion of a segment of DNA causes the entire
strand to be transcribed differently, as is the same with an insertion of a segment in the middle of a strand. Mistakes in
meiosis or mitosis, where a cell divides, can also result in DNA variation and thus, change the individual’s phenotype. In a
nondisjunction, the members of a pair of homologous chromosomes don’t move apart properly during meiosis I or sister
chromatids fail to separate during meiosis II. Because of this, one gamete will receive two of the same chromosome while the
other gamete receives none. An example of this aneuploidy condition is down syndrome, where there is an extra chromosome
in chromosome 21. This mutation causes both developmental and physical phenotypes that would not occur normally.
Changes in genetic variation that cause a detrimental phenotype in the individual will have a negative effect. Only genetic
changes that enhance survival will be carried to the offspring to remain circulating within the population.
M.C. Question: Multiple crosses involving genes known to occur on the same chromosome produce frequencies of
phenotypes that suggest there is a high rate of crossover between these two genes. Which of the following is the most likely
explanation for the phenotypic frequencies observed due to crossing over?
(A) The two genes are far apart from one another.
(B) The two genes are both recessive.
(C) The two genes have incomplete dominance.
(D) The two genes are both located far from the
centromere.
Learning Log/FRQ-style Question: A change in an individual’s
DNA may result in a phenotype that is affected by natural
selection. Describe and explain a situation in which a change
in an organism’s DNA may be beneficial for that organism’s
survival and one in which the mutation would be detrimental.
LO 3.27: The student is able to compare and contrast processes by which genetic variation is produced and
maintained in organisms from multiple domains.
SP 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across
enduring understandings and/or big ideas.
Explanation: Genetic variation within a population is a shared characteristic among organisms that ensures efficient
evolutionary changes. The DNA within a eukaryote must be proofread and the reparation technique of DNA polymerase
further increases the chance of variation among genes. Among an organism’s chromosomes, independent assortment
occurs in Metaphase I of Meiosis, producing a random pairing of chromosomes. The crossing over of chromosomes in
Prophase I ensures genetic variation by creating new chromosome combinations, leading to random fertilization. In
contrast, transformation in prokaryotes leads to recombinant DNA as external DNA is assimilated into the plasmid,
changing the cell’s genotype and phenotype. Transduction along with conjugation lead to genetic recombination as
genetic material is transferred from one cell to the other. Transposition also creates variations as sections of DNA are
moved to different places due to exon shuffling. Reproduction processes that increase genetic variation are essential for
organisms to maintain a population and ensures the success of that population through natural selection.
M.C. Question: What is the role of exon shuffling in providing
genetic diversity to a population?
a) It allows transposons on a section of RNA to copy and
paste itself elsewhere, thus creating different proteins.
b) It causes bacteria to have a recombinant plasmid.
c) It causes new genes to evolve as sections of DNA are
moved to different places.
d) It randomly assorts chromosomes along the Metaphase
plate during Metaphase I of Meiosis.
Learning Log/FRQ-style Question: Suppose you were an expert in
DNA technology and were given the task to insert a gene of interest
into the plasmid of a bacterial cell and clone it. Describe how the
transformation process works. Describe three additional ways in
which bacterial cells become genetically recombinant.
LO 3.28:The Student is able to construct an explanation of the
multiple processes that increase variation within a population.
SP 6.2: The student can construct explanations of phenomena
based on evidence produced
through scientific practices
Explanation: Mutations that naturally occur in DNA replication can change or alter the DNA for future
organisms. The movement of DNA that can take place in Transformation(the taking of raw DNA),
Transduction(the taking in of Viral DNA), Transposition(the movement within it's own sequence of DNA),
or Conjugation(the movement between cells). Sexual reproduction involving random fertilization,
crossing over during the Metaphase of Meiosis, and the random assortment of the chromosomes
during the Metaphase, where the line up across the middle in any order.
MCQ: Which of the following is NOT a way that organisms are assisted in genetic diversity?
A. A disease that was contracted as a child
B. The contraction of a virus
C. Reproduction with a 12th cousin, twice removed
D. Changes in the DNA that occur before birth.
FRQ: Harry contracted a virus as a child which altered DNA,
please explain in detail how this virus altered DNA and
explain how, if so, this would increase diversity if he mated.
LO 3.29: The student is able to construct an explanation of how viruses introduce
genetic variation in host organisms.
6.2 The student can construct explanations of phenomena based on evidence produced through
scientific practice
Explanation: Viruses can introduce genetic variation into bacterial cells via transduction. There are two
different types of transduction: generalized, and specialized. Generalized is done when a phage infects
a cell and makes copies of itself using part of that cells DNA, this is the “donor” cell. Then phages
produced from this cell carry DNA and infect other cells, bringing along the DNA and transferring it
into those cells to make the recombinant cell. In specialized the prophage collects some genetic
material as it exits the chromosome and takes it to a new cell. This is more efficient, but only works
for genes adjacent to the prophage site.
M.C. Question: Which one of these statements is false about Transduction?
A) Transduction can only occur in bacterial cells.
B) Only one cell needs to be infected in order for genetic variation to happen.
C) Specialized transduction happens during the lysogenic cycle.
D) Transduction is not a 100% way to get a certain gene transferred.
Learning Log/FRQ-style Question: While many see viruses as bad, they
through transduction can be used to quickly spread genetic material from
one organism to another. Suppose you are researching which bacteria are
resistant to a virus, using your knowledge of transduction, design an
experiment to find out.
LO 3.30: The student is able to use representations and appropriate models to describe how viral
replication introduces genetic variation in the viral population.
SP 1.4: The student can use representations and models to analyze situations or solve problems
qualitatively and quantitatively.
Explanation: Genetic variation can be introduced in a viral population through mutations during viral replication. For
example, phage viruses replicate via a component assembly model allowing one virus to produce many progeny via the lytic
cycle. Here phages attach to a host cell and phage DNA is injected. The cell’s DNA is hydrolyzed, and phage DNA
commandeers production of phage proteins and copies of the phage genome using host enzymes and components already
within the cell. Sets of proteins assemble to compose phage heads, tails, and tail fibers. The newly completed phages are
released when the phage produces an enzyme to damage the host cell wall, allowing fluid to enter and causing the cell to
burst. Between 100 and 200 phage particles are released with each lysis. As potential bacterial hosts evolve to possess
receptor sites unattractive to phages or develop restriction enzymes that cut up foreign viral DNA, mutations among phages
to resist certain enzymes are favored by natural selection and persist in succeeding generations. Genetic variation can also
occur by way of mutations in RNA viruses that lack error-checking mechanisms and by combination/recombination of
genetic material when related viruses attack the same host cell.
M.C. Question: Lysogenic bacteriophages have the
capacity to transfer a piece of cell DNA adjacent to the
prophage to another cell. This is known as specialized:
A) Invagination
B) Endocytosis
C) Transduction
D) Transformation
1
Attachment.
2
Entry of phage DNA
and degradation of host DNA.
5
Release.
Phage assembly
Learning Log/FRQ-style Question: Consider the case of
an RNA virus: Is genetic variation any more or less likely to
occur than in a similar DNA virus? Explain. Draw and label a
model of the RNA viral reproductive cycle and indicate
where genetic variation is likely to occur.
4
Head Tails Tail fibers
3
Assembly.
Synthesis of viral genomes
and proteins.
LO 3.31: The student is able to describe basic chemical processes for cell communication shared across
evolutionary lines of descent.
SP 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate
in and/or across enduring understandings and/or big ideas.
Explanation: Cells must be able to communicate with other cells in order to respond to their external environment and
successfully thrive in a biological system. The basic chemical processes by which cells communicate are shared across
evolutionary lines of descent, and communication schemes are the products of evolution because correct and
appropriate signal transduction processes are generally under strong selective pressure. Cell communication can range
anywhere from organ differentiation to whole organism physiological responses and behaviors, and these end results
are usually achieved through cell-to-cell contact, plasmodesmata, or receptor-to-recognition protein interaction.
Chemical signaling pathways in cells are determined by the properties of the molecules involved, the concentrations of
signal and receptor molecules, and the binding affinities (fit) between signal and receptor. The signal can be a molecule
or a physical or environmental factor, ultimately resulting in a change in gene expression, protein activity, or
physiological state of the cell or organism, including cell death (apoptosis).
M.C. Question: Which of the following statements concerning cell communication is/are true?
A)The use of pheromones can trigger reproduction and developmental
pathways through cell communication.
B)Apoptosis, programmed cell death, is achieved through a signal cascade that
alters active genes.
C)A signal cascade is initiated when a ligand binds to DNA.
D)Both A and B
Learning Log/FRQ-style Question: Why is it important for cell-to-cell
communication to function quickly and effectively? Why do you think cell
communication in many species functions in very similar ways, and what do
you think would happen to an organism that has dysfunctional signal cascade
pathways?
LO 3.33: The student is able to use representations and appropriate models to describe features of a cell
signaling pathway.
SP 1.4: The student can use representations and models to analyze situations or solve problems
qualitatively and quantitatively.
Explanation: Cell signaling pathways occur in three stages. These three stages are: (signal) reception, (signal)
transduction, and the actual (cellular) response. Reception occurs when the target cell detects a signal
molecule coming from the outside, through which the receptor protein binds at the cell's surface or inside
the cell. Transduction is initiated when the binding molecule alters the shape of the receptor protein,
inducing a specific cellular response. Transduction can occur in one step but often requires a sequence of
steps known as a signal transduction pathway (relay molecules). The response of these specific actions
make sure that the correct activities occur in the appropriate cells, as well as the appropriate time, and
coordination of other cells.
M.C Question: Phosphorylation cascades involving a series of protein kinases are useful for cellular signal
transduction because
A) they are species specific
B) they always lead to the same cellular response because of
specificity
C) they amplify the original signal many-fold
D) they counter the harmful effects of phosphatases by
dephosphorylating proteins
E) the number of molecules is small and fixed
Learning Log? FRQ Style Question: Explain how the binding of a signal molecule to a ligand gated ion
channel affects the distribution of anions and cations in the membrane
LO 3.34: The student is able to construct explanations of cell communication through cell-to-cell direct
contact or through chemical signaling.
SP.2: The student can construct explanations of phenomena based on evidence produced through
scientific practices.
Explanation: Cells are responsible for communicating with other cells through cell-to-cell direct contact, or by
chemical signaling. Communication occurs in various ways in animal cells, including interaction between
immune cells and antigen-presenting cells, helper t-cells and killer t-cells. These living cells interact through
endocrine and paracrine signaling, by using local regulators that target cells, such as Neurotransmitters. These
neurotransmitters are responsible for carrying information from a neuron released by the nerve terminal to
another neuron, by crossing a gap called a synapse that allows the next neuron to receive information at it’s
receptor. In plants, the plasmodesmata is responsible for communicating information between plant cells that
allow material to be transported from cell to cell. The plasmodesmata creates a channel in the cell wall of the
plant cell that allows for information to be passed along to the “attached” cell. With endocrine signaling,
insulin and glucagon work together in keeping blood glucose levels in line. The pancreas releases glucagon
into the bloodstream when blood glucose levels are too low. On the other hand, high levels of blood glucose
causes the body to stimulate insulin into the bloodstream to lower the levels.
M.C. Question: Which of the following is not
an example of endocrine signaling?
A: Parathyroid Glands and Calcium
B: Thyroid glands and iodine
C: Glucagon and Insulin
D: Growth Factors and Clotting factors
E: None of the above
FRQ Style Question: Blood glucose levels decrease
in the bloodstream. Explain the process the body
goes through in order to increase the level back to
normal. If the blood glucose levels would have
increased, what would be the difference?
LO 3.35: The student is able to create representation(s) that depict how cell-to-cell communication occurs by direct
contact or from a distance through chemical signaling.
SP 1.1: The student can create representations and models of natural or man-made phenomena and systems in the
domain
Explanation: Two types of cell to cell communications are illustrated in paracrine (local) and endocrine (long distance) signaling. The 3 stages in
signaling are reception (the ligand or signal molecule binding to a receptor), transduction (converting the signal to a cell response by relay
molecules) and a cell response. Direct cell communications can be illustrated by gap junctions in animals & plasmodesmata in plant cells, and
cell-to-cell recognition. These cell junctions allow for molecules to pass through adjacent cells without crossing the plasma membranes. In
cell-to-cell recognition, two cells may communicate by membrane-bound surface molecules. An example of cell-to-cell recognition is immune
cells interacting by antigen-present cells (APCs) helper-T cells and killer-T cells. Local signaling use local regulators secreted by a cell to
stimulate a target cell's response. Examples of local signaling are paracrine signaling: A secreting cell releases local regulators into into the
extracellular fluid near target cells; and synaptic signaling” never cell releases neurotransmitters into synapses stimulating the target cell or
neuron. Distant cell signaling can be illustrated by hormones and the endocrine system. An endocrine gland releases hormones in 3 different
pathways: simple endocrine, simple neurohormone, and simple neuroendocrine. An illustration of simple endocrine is the pancreas releasing
insulin as a result of low blood glucose. An example of simple neurohormone is suckling stimulating the hypothalamus and posterior pituitary
to release Oxycontin An example of neuroendocrine is the hypothalamus releases a neural and hormonal response to the anterior pituitary to
release another hormone to target cells.
M.C. Question: What is the correct order in which a helper T communicates
with a killer T cell?
1. Killer T cells secrete perforin proteins.
Local signaling
Long-distance signaling
Hypothalamus
2. Killer T cells are activated
3. Killer T cells initiate clone killer T cells
4. Helper T cells activate & secrete cytokines
5.Helper T cell binds to a molecule on a dendritic cell
Anterior
pituitary
6. Helper T cells initiate clone helper T cells
A. 4,5,6,1,2,3
B 2,1,3,4,6,5
C. 5,4,6,2,3,1
D 5,6,4,2,3,1
TSH
Thyroid
E. 6,5,4,2,1,
Learning Log/ FRQ: Name 3 different glands of the endocrine system. Identify
its signaling pathway . Name a hormone of each gland and what various
responses it causes and what it affects
T3+T4
(a) paracrine signaling
(b) Synaptic signaling.
(c) Hormonal signaling.
LO 3.36: The student is able to describe a model that expresses the key elements of signal
transduction pathways by which a signal is converted to a cellular response.
SP 1.5: The student can reexpress key elements of natural phenomena across multiple
representations in the domain.
Explanation: In cell communication, signal molecules such as hormones are received by cells to
carry out a cellular response. The 3 stages of cell signaling are reception, transduction, and
response. In reception, the ligand binds to a receptor; these receptors include intracellular
receptors, G-protein-linked receptors, tyrosine kinase receptors, and ligand-gated ion channels ,
each creating a unique cell response. In transduction, the signal from reception is converted to a
specific cellular response often by protein phosphorylations and then 2nd messengers that
deliver the final cell response which may include enzyme activation or gene transcription.
M.C. Question: Which of the following statements concerning signal receptors is true?
A) An intracellular receptor may receive polar hormones.
B) ATP displaces ADP to activate the G-protein after reception.
C) Tyrosine kinase receptors form a phosphorylated dimer to activate relay proteins.
D) Ligand-gated ion channels allow ions to flow against the concentration gradient.
Learning Log/FRQ-style Question: Describe
in detail the process by which epinephrine
triggers a cell response. Be sure to include
reception, transduction, and cell response.
•
•
•
•
•
•
•
•
LO 3.38 The student is able to describe a model that expresses key elements to show how change in signal transduction can alter
cellular response.
SP 1.5 The student can reexpress key elements of natural phenomena across multiple
representations in the domain.
Explanation:
Signal transduction is defined as the ability of a cell to change
behavior in response to a receptor-ligand interaction.
The ligand is the primary messenger.
As the result of binding the receptor, other molecules or
second messengers are produced within the target cell.
Second messengers relay the signal from one location to
another (such as from plasma membrane to nucleus).
Often a cascade of changes occur within the cell which
results in a change in the cell’s function or identity.
The signal transduction pathway can act to amplify the
cellular response to an external signal.
Messenger molecules may be amino acids, peptides,
proteins, fatty acids, lipids, nucleosides or nucleotides.
Hydrophilic messengers bind to cell membrane receptors.
Hydrophobic messengers bind to intracellular receptors
which regulate expression of specific genes. So, changes in
signal transduction will completely alter the cellular
response.
Multiple choice:
In signal transduction, if the receptor is altered, which of
the following will happen? a) the cellular response will go on
as normal b) there will be a different cellular response c) the
cell will stop all functions d) the cell will burst.
FRQ:
A) Describe the basic principles of signal transduction.
B) Think of 3 examples of signal transduction receptors.
C) Compare and contrast 2 of the examples of signal
transduction receptors.
LO 3.39: The Student is able to construct an explanation of how certain drugs affect
signal reception and, consequently, signal transduction pathways.
SP 6.2: The student can construct explanations of phenomena based on evidence
produced through scientific practices.
Explanation: Certain drugs such as opiates mimic the shapes of
ligands, which bind to the specific ligand receptors. This
mimicry prevents the naturally produced neurotransmitters
from binding to the receptor site. As more and more of the
opiate is absorbed the body stops making the natural
chemical which leads to addiction and withdrawal when the
artificial chemical is no longer absorbed.
M.C. Question: Suppose a healthy individual who has never used a
morphine based drug decided to inject themselves with
heroin. How would the body react to the initial injection?
A.) The individual would receive the instant gratification of a high
with few residual symptoms.
B.) The individual would experience nausea and vomiting due to the
sudden chemical imbalance in the nervous system.
C.) The individual would experience cross tolerance and would feel
little to no effect from the drug.
D.) The morphine ligand would not be able to bind to the receptor
site and would have no effect on the individual.
E.) The drug would immediately show inhibitory effects causing the
individual to feel sluggish and uncaring.
Learning Log/FRQ Question: In the body natural endorphin acts as
a natural stimulant and pain reliever. Endorphins can inhibit
neurons from firing and create a natural analgesic affect or
excite the neurons which gives the organism a feeling of
euphoria. In a recently recovering heroin addict, how would
the body be affected if the person went through a vigorous
workout?
•
•
•
LO 3.40- The student is able to create a representation that
describes how organisms exchange information in response to
internal changes and external cues, and which can result in
changes in behavior.
SP 1.1- The student can analyze data to identify patterns or
relationships.
Explanation: Behavior is everything an animal does and how it
does it. It is separated into two categories for causes:
proximate(nature) and ultimate(nurture). Breeding times,
physiological adaptations to environments and more are all
proximate observations. Specific behaviors such as fixed action
patterns (red stimuli induces attacks in male stickleback fish),
imprinting (young geese during a critical period follow initial
stimuli of an organism moving away),and communication (round
and waggle dances in honeybees) are characterized as innate, or
strongly-genetically induced. Learned behaviors are responses to
environmental stimuli, as is seen in operant , where responses are
voluntary, and classical conditioning, where responses are
involuntary. Consider Pavlov’s bell experiment and the navigation
of mice through a maze, respectively. The dog salivated
subconsciously after associating the bell ring with food and the
mice after multiple trials-and-errors, learned to consciously locate
the food at the end of a maze.
Dry open area
Which of the following is a behavioral pattern resulting from an ultimate
cause?
A) A male robin attacks a red tennis ball because it resembles the breast
of another male.
B) A male robin attacks a red tennis ball because hormonal changes in
spring increase its aggression.
C) A male robin attacks a red tennis ball because a part of its brain is
stimulated by red objects.
D) A male robin attacks a red tennis ball because several times in the
past red tennis balls have been thrown at it, and it has learned that they
are dangerous.
E) A male robin attacks a red tennis ball because it confuses it with an
encroaching male who will steal his territory.
FRQ:
Without adaptive behaviors, animals would not survive.
(a) Describe what innate and learned behaviors are. Explain the
adaptive value of each of these two categories of behavior to an
individual animal.
(b) During mating season, male snakes exhibit tracking behavior when
they follow chemical pheromone trails deposited on the ground by
females. Design a controlled experiment to determine whether a male
garter snake will track only a female of his species or will also follow the
female of a related species.
Moist site under
leaf
(a) Kinesis increases the chance that a sow bug will encounter and stay in a moist environment.
Direction of
current
(b) Positive rheotaxis keeps trout facing into the current, the direction from which most food
comes.
LO 3.41 The student is able to create a representation that describes how organisms exchange information in
response to internal changes and external cues, and which can result in changes in behavior.
SP 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain.
Explanation: Responses are dependent upon or influenced by underlying genetic information, and decoding in
many cases is complex and affected by external conditions. For example, biological rhythms, mating behaviors,
flowering, animal communications and social structures are dependent on and elicited by external signals and may
encompass a range of responses and behaviors. Organ systems have evolved that sense and process external
information to facilitate and enhance survival, growth and reproduction in multicellular organisms. These include
sensory systems that monitor and detect physical and chemical signals from the environment and other individuals
in the population and that influence an animal’s well-being. Individual behavior influences population behavior, and
both are the products of information recognition, processing and transmission. Communication among individuals
within a population may increase the long-term success of the population. Responses to information and
communication of information are vital to natural selection and evolution.
MC: How is the distance to a food source communicated
by a dancing honeybee?
A)by the direction it waggles its abdomen
B)by how far it moves during the straight run portion
of the dance
C)by which direction it turns after making the straight run
D)by the tempo or degree of vigor of the dance
E)none of the above - bees can't communicate the distance
Animals use many forms of communication to
indicate dominance, find food, establish territory
and ensure reproductive success. Describe how an
animal can use audible, and chemical signals to
transfer information. Include two examples in your
answer.
LO 3.42: The student is able to describe how organisms exchange information in response to internal changes or
environmental cues.
SP 7.1: The student can connect phenomena and models across spatial and temporal scales.
Explanation: Organisms exchange information by the traveling of neurons across the synapses. A neuron has a cell body,
axons and dendrites. Axons are long threadlike parts of the nerve cell where impulses are carried. Many axons have a
cover over them called a myelin sheath that acts as an electrical insulator. The myelin sheaths are made of cells called
Schwann Cells. There are gaps in the myelin sheath called the Nodes of Ranvier. This is where the signal bounces from
node to node. When Na+ ions come into the cell, the cell becomes less negative. When the cell becomes less negative it is
called depolarized. The action potential is when more Na+ ions enter the cell and the nerve impulse is started. When K+
ions leave the cell, the cell becomes more negative. When the cell becomes less negative it is called hyperpolarization.
The normal charge of a neuron is -70 mV; when the action potential is met and the threshold is achieved, the charge is -55
mV. After the threshold has been reached and the nerve impulse has finished, the sodium potassium pumps open and
restore the system back to -70 mV by active transport.
M.C. Question: After the action potential of a neuron, which of the following restores the cell to -70 mV?
a) decrease in Na+ concentration
b) increase in K+ concentration
c) Aquaporins
d) Sodium potassium pumps
e) None of the above
Learning Log/ FRQ-style Question: Suppose you place a neuron in an aqueous solution containing free Na+ and K+ ions.
Thresholds are reached and action potentials are created. Why does the action potential only travel in one direction?
After the cell is restored to normal charge, how does a single neuron interpret multiple inputs?
AP Biology Exam Review: Learning Objective Focus
(A) LO 3.43: The student is able to construct an explanation, based on scientific theories and models, about how nervous systems detect external and internal signals,
transmit and integrate information and produce responses.
(B) SP 6.2: Student can construct explanations of phenomena based on evidenced produced through scientific practices
(C)Explanation: When an external or internal signal is received, sensory cells convert stimuli into action potentials. Nerve impulses/action potentials are received
through the Dendrite of a pre-synaptic region of a neuron and transmitted to other cells through the axon of the neuron. At the end of the axon is called the axon
terminals, this is where neuron may make contact with the dendrites of another neuron, with a receptor/effector. Receptors are sensory neurons in that receive
stimuli from the external environment. The points of contact at which impulses are passed from one cell to another are known as the synaptic cleft,
neurotransmitters are found inside. Neurotransmitters, chemical substances that are used to by one neuron to signal another. Nerve impulses are electrical as they
move along the nerve and chemical as they travel over the synaptic cleft. After sensory neurons carry impulses they eventually reach the brain. The brain acts to
interpret, sort, and process the incoming impulses and then produce on a response.
(D)Multiple choice:
•A women gets in a car accident and suffers from nerve damage in her right arm. After analyzing the injuries, the doctor concluded that a dendrite in her nerve
cells has been severed. What will most likely be the effect of this damage?
•A. There will be no interruption of her nerve signaling and she will have full range of motion in her arm.
•B. There will be no longer term effects; the dendrite will self-heal after 1-2 weeks and she will regain full motion
•C. She will permanently lose motion in her entire upper body; damage to one dendrite will interrupt signaling in her upper body region
•D. She will l permanently lose motion in her right arm, the damage to the dendrite will make it so that signals will be unable to travel through the right arm’s
nervous system
•E. She will temporarily lose motion in her right arm; the damage to the dendrite will have a direct effect on the axon of nerve cells in her right arm causing her
nerve cells to be able to signal to other nerve cells temporarily
(E) FRQ-Suppose a ball is thrown toward your head and you react by catching the ball, describe the process of your body transmitting the signal (the sight of the ball
flying towards you) and how your nervous system processes this information and produces a response to it.
LO 3.44: The student is able to describe how nervous systems detect external and internal signals
SP 1.2: The student can describe representations and models of natural or man-made phenomena and systems in the domain
Explanation: The sensory nerve system (SNS) acts as an input device, transmitting information from all parts of the body
to the central nervous system (CNS) through signals. Afferent (sensory) neurons carry these sensory signals from end
organs to the CNS for processing and integration, by conducting impulses into the brain or spinal cord. End organs
include muscles, glands, specialized senses, and skins, all which contain afferent neurons. The CNS then acts as a
processing unit, where information is received, processed, and commands are issued for the response. The signals issued
by the sensory neurons are transmitted through electrical and chemical signals. A nerve cell membrane at rest measures
-70 mV, so the electrical charge outside the membrane is positive when the cell membrane is unstimulated, creating a
resting membrane potential. However, when a nerve impulse causes the of channel proteins and the flow of Na+ ions
into the cell, while K ions remain outside the membrane, a threshold value of -50 mV is reached. This causes ion gates in
the membrane to open, allowing Na+ to rush into the cell and create an action potential, so a signal is sent from the
sensory neurons to the CNS.
M.C. Question: Action potentials are normally
carried in one direction from the axon hillock to
the axon terminals. By using an electron probe,
you experimentally depolarize the middle of the
axon to threshold. What do you expect?
a. No action potential will be initiated.
b. An action potential will be initiated and
proceed in the normal direction toward the axon
terminal.
c. An action potential will be initiated and proceed
back toward the axon hillock.
d. Two action potentials will be initiated, one
going toward the axon terminal and one going
back toward the hillock.
e. An action potential will be initiated, but it will
die out before it reaches the axon terminal.
Learning Log/FRQ-Style Question: Ouabain, a plant substance used
in some cultures to poison hunting arrows, disables the sodiumpotassium pump. What change in the resting membrane potential
would you expect to see if you treated a neuron with ouabain? Why?
LO 3.45: The student is able to describe how nervous systems transmit information.
SP 1.2: The student can describe representations and models of natural or man-made phenomena and
systems in the domain.
Explanation: Animals nervous systems are made up of Central Nervous System (CNS) and Peripheral
Nervous System (PNS). A signal is usually detected by PNS and sent to CNS which provides a response
to be carried out by PNS. A neuron is the basic structure of Nervous Systems. Action potentials
propagate electrical impulses along neurons when they reach the threshold and depolarize the
membrane. The impulse triggers the cell to release certain chemical messengers called
neurotransmitters to the adjacent cell across the synapse to produce a response which is either
inhibitory or stimulatory.
M.C. Question: Which of the following is the correct
of sequence?
A) Resting state – depolarization – Na+ influx – K+ efflux
B) Na+ influx – depolarization – K+ efflux – resting state
C) Resting state – K+ efflux – Na+ influx – depolarization
D) K+ efflux – resting state – Na+ influx – depolarization
Learning Log/FRQ-style Question: Describe in
details what happens between a presynaptic cell
and a postsynaptic cell using the following terms:
voltage-gated Ca2+ channel, Ca2+, synaptic vesicles,
Na+/K+, ligand-gated ion channels, and neurotransmitters.
order
LO 3.46: The student is able to describe how the vertebrate brain integrates information to produce a response.
SP 1.2: The student can describe representations and models of natural or man-made
phenomena and systems in the domain.
Explanation: The brain provides the integrative power that underlies the complex behavior of vertebrates. The spinal cord
integrates simple responses to certain kinds of stimuli (such as the knee-jerk reflex) and conveys the information to and from the
brain. When the brain receives information, it is immediately processed. Sensory neurons transmit information from sensors that
detect external stimuli (light, sound, heat, smell, and taste) and internal conditions (such as blood pressure, blood carbon dioxide
level, and muscle tension). The information is sent to the CNS, where interneurons integrate the sensory input. Motor output
leaves the CNS via motor neurons, which communicate with effector cells (muscle cells or endocrine cells).When experiencing a
reflex, for example, the information is first received by dendrites extending from the cell body of the neuron. The signal is then
generated at the axon hillock and transmits down the axon itself. At the end of the neuron, there are synaptic terminals, where the
information is passed from the transmitting neuron (the presynaptic cell) to the receiving cell (the postsynaptic cell) by means of
chemical messengers called neurotransmitters throughout the brain. These neurotransmitters in the presynaptic neurons bind to
receptors in the postsynaptic neurons, and pass the signal onward. The sensory neurons convey the information to the spinal cord.
They then communicate with interneurons that both inhibit and signal certain motor neurons that convey signals to a specific body
part, producing a response.
M.C. Question: If the axon of a neuron was to be severed, what would
most likely be the effect?
A) The neuron would be unable to receive information from another
neuron.
B) The neuron would be unable to transmit information to another
neuron.
C) It would have no effect, depending on which side of the axon that
was severed.
D) The myelin sheath would break and the transmittance would slow
down.
Learning Log/FRQ-style Question: It’s Halloween night and you go to
a haunted house. While you are there, a masked character runs out and
scares you. Without thinking, you punch the character in the face.
This is considered a type of reflex. How does your brain integrate the
information of fright and produce a response? How is this response
created through the pathway of neurons and neurotransmitters? Be
specific.
LO 3.47 The student is able to create a visual representation of complex nervous systems to describe and
explain how these systems detect external and internal signals, transmit and integrate information, and
produce responses.
SP 1.1 The student create representations and models of natural or man-made phenomena and systems in
the domain.
Explanation: The neuron is the basic structure of the nervous system. It is comprised of an axon, cell body, and dendrites.
External and internal signals send nerve signals through neurons from the peripheral nervous system to the central nervous
system. A signal arrives at the dendrites , passes through the cell body and, if the signal reaches action potential, passes
through the axon hillock and finally goes to the axon so that it can carry on the signal to another neuron. A signal reaches
action potential if the membrane of the neuron is depolarized. The membrane of a neuron becomes depolarized if, after
receiving a stimulus, sodium gated channels powered by ATP allow sodium ions to enter and cause a rise in the membrane
potential. As a result, the rapid influx of sodium ions allows the polarity of the neuron membrane to be reversed. Potassium
channels powered by ATP are also activated and they flow out of the cell, allowing for the action potential to return to resting
potential. This entire action potential process allows for a response to occur that could include the release of excitatory or
inhibitory neurotransmitters like GABA or acetylcholine or the transferring of a message from one neuron to the other
through the synaptic gap, which would, in the end, allow for a physical response through motor neurons in the peripheral
nervous system.
M.C. Question: Why are action potentials usually conducted in
only one direction along an axon?
A. The nodes of Ranvier can conduct potentials in only one
direction.
B. The brief refractory period prevents reopening of voltagegated Na+ channels.
C. The axon hillock has a higher membrane potential than the
terminals of the axon.
D. Ions can flow in only one direction
Learning Log/FRQ Style Question: If all the Ca+2 in the fluid
surrounding a neuron were removed, how would this affect
the transmission of information within and between neurons?
Why?
LO 3.48: The student is able to create a visual representation to describe how nervous systems detect external
and internal signals.
SP 1.1: The student can create representations and models of natural or man-made
phenomena and systems in the domain.
Explanation: For survival, an animal’s nervous system must detect external stimuli, process, and then respond to such
stimuli accordingly. Sensory systems within the body have developed the ability to monitor and detect chemical and
physical signals from the environment. The NS then interacts with these sensory and internal body systems to produce
appropriate responses, from alterations in metabolic rate to triggering respiration. Nervous systems receive external
information via sensory neurons, associated with the 5 senses, which consist of dendrites, a cell body, and an axon.
Electrical signals generate impulses within these neurons through the creation of action potentials, in which Na+ and K+
gated ion channels open, allowing the neuron to become temporarily depolarized. Information is transferred from one
neuron to the next via the movement of neurotransmitters, chemical signals, across a synapse. Transmission of this
information results in a response, directed by the brain, that will call for changes in the body, whether it be, for example,
muscle movement or hormone release.
M.C. Question: Suppose you were to draw an image of a neuron
that had just received an electrical impulse. Which of the
following would not be included in your drawing? Why?
a) Neurotransmitters, because they are not involved in nerve
signaling.
b) Nothing. It is a chemical signal that travels down a neuron,
not an electrical one.
c) ATP synthase, because neurons are not directly responsible
for energy production.
d) Mitochondrion, because neurons do not have the organelles
that regular cells have.
FRQ: Explain how a gazelle is able to run when
being chased by a cheetah in terms of the nervous
system response, and draw and label a visual
representation of a nerve cell involved in the
response.
L
LO 3.49 :The student is able to create a visual representation to describe how nervous systems transmit information.
SP 1.1: The student can create representations and models of natural or man-made phenomena and systems in the domain
Explanation: The basic structure and function in the nervous system is called the neuron. Neuron is a long cell that consists of a cell
body, dendrites and axon. The nervous system consists of central nervous system and peripheral nervous system. PNS carries
impulses between the CNS and body. The nerve cells can be divided into three main classes. There are sensory neurons,
interneuron and motor neurons. For instance when the body receives a stimuli, the touch stimulates sensory receptors located in
skin which send a sensory impulse that is carried to the spinal cord. Interneuron process incoming impulses and pass response to
the motor neurons. Motor neurons carry the response away from the brain and spinal cord to a muscle or gland. However, the
impulses need to be transmitted from one nerve cell to another for it to be interpreted into a response. When a stimulus excites a
neuron, gated sodium channels in the membrane open up. This allows sodium ions to enter the cell. The buildup of positive sodium
ions inside the membrane causes the cell to become more positively charged inside than outside. Therefore, this cell is
depolarized. If threshold potential is reached, and action potential is triggered. This causes potassium channels to open slowly. Na
and K pumps are powered by ATP. After a while, the sodium gates slowly closes and potassium rushes out causing depolarization.
Then the potassium channels slowly close. The impulse then moves to the end of the axon. Here the calcium channels open,
allowing calcium to enter the end of the axon, the calcium causes vesicles in the axon to fuse with the plasma membrane,
releasing their chemicals (neurotransmitters) into the synaptic space. The neurotransmitters diffuse across the space to the
dendrites of the next neuron, this signals receptor sites to open the ion channels. The open channels change the polarity in the
neuron, starting a new impulse. Myelin sheath insulates the axons increasing the speed at which the signal travels. The
transmission of the impulses through nerve cells will cause a response to be elicited.
M.C. Question : Transmission across a synapse is achieved mainly by a diffusion of neurotransmitter across the cleft
which is triggered specifically by?
a)
The depolarization of membrane
b)
The influx of Ca+ into the axon of sending neuron
c)
The initial resting potential of the neuron
d)
The insulation of axons by Schwann cells
FRQ- style question : Determine the function(s) of CA2+ in the transmission of
signals between neurons. How would the removal of CA+ from the synaptic cleft affect the way the
signals are transmitted?
LO 3.50: The student is able to create a visual representation to describe how the vertebrate brain
integrates information to produce a response.
SP 1.1 The student can create representations and models of natural or man-made phenomena and
systems in the domain.
Explanation: The nervous system undergoes three stages controlled by specific neurons while processing information. The
first stage involves sensory neurons which take the information from the body’s sensors that detect a stimulus. These
neurons can be triggered by external sources such as light or sound or by internal sources such as blood pressure changes.
This sensory input is then transferred to the interneurons which analyze and interpret the information by taking into
account the present and past situations. Once integrated, motor neurons are activated which work with effector cells to
provoke a response from muscles. Neurons stay in resting potential until a stimulus causes sodium ions to flow into the cell,
thus causing the usually negative internal area to become more positive. The cell is then depolarized and it is in action
potential. Once the threshold is met, the signal is sent from the neuron to a neighboring receiving neuron. Potassium ions
then flood out of the cell to repolarize it back to resting potential.
M.C. Question: Which of the following cells are involved after the information is transferred to the CNS?
A) The sensory cells are sent by the sensory neurons to
transfer the information to be integrated by the
interneurons
B) The sensory cells are sent by the sensory neurons to
stimulate muscles after information is processed by
interneurons
C) The effector cells are sent by the motor neurons to
transfer the information to be integrated by the
interneurons
D) The effector cells are sent by the motor neurons to
stimulate muscles after the information has been
processed by the interneurons
Learning Log/FRQ-style Question: Suppose that a
doctor’s patient got into an accident in which her
sensory neurons were damaged. How would the
entire integration process be effected? Would a
response still be elicited from a stimulus?