EOC Review Part 2: Heredity-Organisms reproduce and transmit hereditary information
SPI 3210.4.1 Identify the structure and function of DNA
SPI 3210.4.2 Associate the process of DNA replication with its biological significance
SPI 3210.4.3 Recognize the interactions between DNA and RNA during protein synthesis
SPI 3210.4.4 Determine the probability of a particular trait in an offspring based on the genotype of the
parents mode of inheritance
SPI 3210.4.5 Apply pedigree data to interpret various modes of genetic inheritance
SPI 3210.4.6 Describe how meiosis is involved in the production of egg and sperm cells
SPI 3210.1.6 Determine the relationship between cell growth and cell reproduction
DNA and RNA: nucleic acids are composed of nucleotides; nucleotides are made of a phosphate group,
sugar, and nitrogenous base
Draw and label a nucleotide for DNA and a nucleotide for RNA
Central Dogma of Biology: DNA -----(transcription)→RNA -----(translation)-----→Protein
DNA: deoxyribonucleic acid; it is double stranded and a twisted helix shape; it never leaves the nucleus
(except when nucleus disappears during cell division); nitrogenous bases include (A) Adenine, (T) thymine,
(G) guanine, and (C) cytosine; rules of base pairing say that G goes with C and A goes with T; purines
(double ring structures pair with pyrimidines single ring structures); A and G are purines and C and T are
pyrimidines; weak hydrogen bonds hold the pairs of nitrogen bases together and are easily broken; sugar is
deoxyribose; contains instructions for production of all proteins for an organism
DNA Replication: DNA uncoils and each strand serves as a template to make a new copy; when the cell is
not dividing the DNA is in the form of chromatin; when it divides the duplicated DNA forms duplicated
chromosomes (sister chromatids); DNA helicase(uncoils), DNA polymerase(brings in new nucleotides), and
DNA ligase(joins dna fragments called Okazaki fragments) are enzymes that facilitate copying of DNA
RNA: ribonucleic acid; single stranded and various shapes; leaves the nucleus; nitrogenous bases include (A)
adenine, (U) uracil, (G) guanine and (C) cytosine; sugar is ribose; three types of RNA are (1)
mRNA=messenger RNA (2) rRNA= ribosomal RNA (3) tRNA = transfer RNA
Protein synthesis: proteins are produced from the information in DNA; two parts (1) Transcription- mRNA
is made from the sense strand of the DNA and carries the message out of the nucleus to the ribosomes and
(2) translation-message carried by the mRNA is translated/decoded by the rRNA at the ribosomes to the
sequence of amino acids needed to make the protein; tRNA (transfer RNA) transfers the amino acids from
the cytoplasm to the ribosomes to construct the polypeptide or protein.
Copy and label diagram of DNA; Copy and label Protein synthesis diagram
Asexual vs. sexual reproduction:
Asexual reproduction: a single parent produces one or more identical offspring by dividing into two cells
(mitosis or “binary fission in bacteria, “budding” in fungi); offspring are “clones” of parent (genetically
identical); common form of reproduction in unicellular organisms; quick process that requires little energy;
produces large number of offspring
Sexual reproduction: involves the production and fusion of two haploid sex cells (gametes) produced during
a process called meiosis; sperm is the male cell and ova (egg) from the female join during a process called
“fertilization” which results in a diploid cell called a “zygote”; usually will then reproduce cells to create a
multicellular organism through mitosis; fertilization can be internal (dogs and people) or external (most
fish); slow process that requires a great deal of cellular energy; few offspring are produced
Cell division:
Process of copying and dividing the entire cell; the cell grows, prepares for division, and then divides to form
daughter cells; (1) mitosis/binary fission in bacteria and (2) meiosis
Cell cycle will include Interphase, mitosis and Cytokinesis
Interphase- longest phase of the cell cycle; the cell grows; normal activities and metabolism take place;
duplicates the DNA and prepares for division
Mitosis- division of the nucleus of the cell
Prophase- duplicated chromosomes form by coiling of chromatin and spindle fibers appear; nuclear
membrane disappeared.
Metaphase- duplicated chromosomes line up along the equator of the cell between spindle fibers
Anaphase-duplicated chromosomes pulled apart (chromatids) to opposite ends of the cell
Telophase-nuclear membrane reforms around chromosomes at each end of the cell; spindle fibers
disappear; chromosomes uncoil to chromatin
Cytokinesis: division of the plasma membrane and cytoplasm; two daughter cells are formed with exact
genetic information
Results of mitosis are two daughter cells(body cells or somatic cells) with the same number of chromosomes
as original cell (humans this number is 46); these cells are called diploid and contain two of every
chromosome (23 pairs in humans)
Meiosis: consists of two cell divisions, but only one DNA replication; often referred to as “reduction
division”; each cell division has prophase, metaphase, anaphase, telophase and Cytokinesis; only one
interphase at the beginning; only occurs in the formation of sex cells (gametes); each are genetically unique
thanks to crossing over and independent assortment of the chromosomes.
First division: produces cells with the have number (1/2) chromosomes but all are still duplicated
Second division: produces a total of 4 haploid cells (one of every chromosome)= sex cells (gametes)
These sex cells (sperm and egg) unite during fertilization to form a zygote (diploid cell) that will develop into
an individual organism
Copy diagrams and information for mitosis and meiosis
Genetics: the branch of biology hat deals with inheritance of traits from generation to generation (heredity)
Gregor Mendel experimented with sweet pea plants in the 1800s; he is known as the Father of Modern
Genetics.
Trait-characteristic an individual receives from its parent(s)
Gene- segment of DNA that carries instructions responsible for expression of traits; different forms
of a gene are called “alleles”
Homozygous- refers to two alleles of a pair that are identical in the zygote (ex. BB or bb) “purebred”
Heterozygous- refers to two alleles of a pair that are different in the zygote (ex. Bb) “hybrid”
Dominant- controlling allele; covers or hides the other allele for a trait; represented by capital letter
Recessive- hidden allele, designated with a lower case letter
Genotype- genetic makeup of an organism; type of genes received (ex. Bb, BB, or bb)
Phenotype- physical appearance of an organism (ex. Brown or white)
Monohybrid- cross involving one trait (use small Punnett square 4 boxes)
Dihybrid- cross involving two traits at the same time (use large Punnett square 16 boxes)
Copy sample Punnett squares
Punnett square- graphic organizer to show the probable results of a genetic cross (mating)
Pedigree chart- graphic organizer to map genetic traits from generation to generation
Autosomal recessive: trait occurs equally in both sexes; trait tends to skip a generation;
affected offspring usually born to parents that are unaffected (normal); if both parents
are affected then all the offspring must have it as well
Autosomal dominant: trait occurs equally in both sexes; does not skip a generation;
if offspring has it at least one parent should be affected as well; if neither parent has
the trait then none of the offspring can be affected
Sex-linked recessive: occurs more frequently in males than females; affected males usually
have unaffected mothers; appears to skip a generation; never passed from father to son
because it is on the X chromosomes; if a girl is affected her father had to be affected too
Y-linked: only males can be affected because it is on the Y chromosome; if the father is
affected then all of his sons must be affected as well; does not skip a generation
Copy pedigree charts and analyze
Karyotype- chart of chromosomes of an individual grouped in their homologous pairs to study
chromosome number/disorders (like Down’s syndrome trisomy 21-extra chromosome)
(turners syndrome- monosomy- missing and x in a female)
Copy the karyotype; is the individual a boy or a girl? Any abnormalities?
Test Cross- mating of an individual of unknown genotype (either pure for dominant or hybrid) with
and individual of known genotype (pure recessive) to help determine the unknown
genotype (if hybrid some recessives will be present in offspring, no recessives = pure)
Mendel’s Laws of Inheritance:
(1) Law of dominance says that the dominant allele will prevent the other allele (recessive)
from being expressed
(2) Law of segregation says that gene pairs separate when gametes (sex cells) are formed
during meiosis; each cell will only have one allele of each gene pair
(3) Law of independent assortment says that different pairs of genes separate independently
of each other when gametes are formed during metaphase/anaphase II of meiosis
Patterns of inheritance:
Sex chromosomes are the 23rd pair; XX = female XY= male
Sex-linked traits are traits with a gene located on either the X or Y chromosome and is therefore
associated with a particular gender (male or female); examples of traits: colorblindness,
patterned baldness, and hemophilia
Linked traits are those whose genes are close together on the same chromosome and are therefore
usually inherited together; ex. Red hair and freckles
Multiple alleles occur when there are more than two alleles for a given trait (blood type A,B, O)
Polygene inheritance is when one trait is controlled by many genes; ex. Height, skin color, hair color
range of phenotypes gradually changes.
Codominance is where homozygous parents for different traits result in offspring that show both
traits equally; black chicken crossed with white chicken produces a checkered chicken
Incomplete dominance is where the hybrid results in a phenotype that is in between the two
phenotypes of the pure individuals; red crossed with white produces a pink offspring
Variation in offspring can be attributed to:
(1) crossing over- genes from one chromosome are exchanged with genes from another chromosome
Occurs regularly during meiosis (prophase I)
(2) nondisjunction- during meiosis the homologous pairs of chromosomes don’t separate; results
in cells that either have an extra chromosome or missing a chromosome; if fertilization occurs
the zygote formed will have a trisomy (extra chromosome like Downs) or monosomy (missing
a chromosome like Turners)
(3) Independent assortment of chromosomes as they are lined up during meiosis II; random
Mutations are changes in the genetic code; only passed to offspring if occur in gamete (sex cell); most
mutations have no effect; can be spontaneous of caused by mutagens (ex. Radiation, chemicals)
Gene mutations will affect only one gene; frame shift or substitution; can be missense, nonsense,
silent mutations
Chromosome mutations affect many genes on a chromosome- inversion, translocation, deletion,
Duplication, etc.
Look at chart for mutation types. You do not need to copy this into your notes but should make
Make notations for each type that will help you remember them.
1. Which statement describes the structure of DNA? (c)
a. a single strand of amino acids
b. a single strand of nucleotides
c. a double strand of nucleotides
d. a double strand of amino acids
2. DNA is the information storage molecule of the cell. This infomraiton provides the instructions to
produce molecules used for cellular activities. Which diagram best illustrates the translation of DNA’s
encoded instructions? (d)
3. If one side of the DNA reads AGAGTC then what will the other side read? (TCTCAG)
4. Growth rate, length of bones, muscle structure, andhormone levels may all affect human height. Each of
these factors is controlled by many different proteins in body cells. What type of gene relationship controls
human body height? (polygene intheritance)
5. DNA is replicated during the interphase of the cell cycle. Which event is needed to ensure the normal
number of chromosomes is present in both daughter cells? (mitosis- division of the nucleus)
6. DNA transcribes the information for protein synthesis in mRNA. Where does the process of transcription
take place? (in the nucleus)
7. Proteins are produced during translation. Which molecule carries the protein code that is translated?
(mRNA)
8. Hemophilia is a sex-linked genetic disease. If a male with hemophilia and a homozygous normal female
have a female child, what is the probability that the child will be a carrier for hemophilia? (0%)
9. In snapdragons, if white flowers are crossed with red flowers, all the offspring have pink flowers. When
two pink snapdragons are crossed, some offspring have white flowers, some have red flowers, and some
have pink flowers. Which inheritance pattern do snapdragon flowers exhibit? (incomplete dominance)
10. What pattern of inheritance is shown in this pedigree? (autosomal dominant)
11. Gametes contain hald the number of chromosomes that other cells in the body contain. When are
gametes produced in organisms? (during meiosis)
12. Why is meiosis important for sexual reproduction? (meiosis reduces the number of chromosomes)
13.Chronic myeloid leukemia is caused by a chromosomal mutation. An example of this mutation is shown
in the diagram. What type of chromosomal mutation causes myeloid leukemia? (translocation)
14. Which process is attributed to causing an additional 21st chromosome in a human karyotype?
(nondisjunction)
15. Through scientific research, genetic technologies have advanced the study of gene sequences. Which is
a main benefit of gene therapy technology? (a)
a. the ability to cure genetic diseases by replacing defective genes
b. the ability to genetically design organsisms that have never existed
c. understanding how human genes turn on and off to make carbohydrates
d. making genetically superior plants and animals to benefit the entire world
16. The bases in DNA pair by chemical interactions. How are the base pairs formed differently between the
pairs? (a)
a. adenine and thymine form two hydrogen bonds, while cytosine and guanine form three hydrogen
bonds
b. adenine and thymine form three hydrogen bonds, while cytosine and guanine form two hydrogen
bonds
c. adenine and thymine form covalent bonds, while cytosine and guanine form hydrogen bonds
d. adenine and thymine form hydrogen bonds, while cytosine and guanine form covalent bonds
17. DNA contains four different nitrogenous bases. Which base always pairs with guanine in the DNA
molecule? (cytosine)
18. A portion of DNA is transcribed into the mRNA sequence AUGUCAAGCGUA. The table below shows the
amino acids that correspond to codons in an mRNA sequence. Decode the mRNA sequence.
(Methionine(start)-serine-serine-valine)
19. What meiotic stage produces the haploid condition of the four daughter cells? (division 1)
20. What is the end result of meiosis? (four haploid cells)
21. What event during meiosis introduces genetic variation between parents and offspring? (crossing over)
22.In the United States, it is possible for discoverers of gene sequences in organisms to patent those
sequences. This gies the discoverer property rights for the sequences. Many scientists object to this
practice. Which is the strongest argument against allowing a gene sequence to be patented? (c)
a. Patenting sequences prevents the sequences from being expressed in nature.
b. Patenting sequences prevents the sequences from being used in genetically modified organisms.
c. Patenting sequences prevents researchers from studying and creating innovations from the
patented sequences.
d. Patenting sequences prevents conservationists from understanding the ecological needs of
organisms from which the patented sequences come.
23. There is broad public debate on the ethics of performing research on human stem cells to find cures for
human diseases. Which statement describes an ethical issue about the use of human stem cells for
research? (a)
a. Some research focuses on stem cells obtained through the destruction of human embryos.
b. Any treatments discovered through such research would likely be too expensive for many.
c. Some research focuses on therapies that would only benefit the person from whom the stem
cells came.
d. Any treatments dsicvoered through such research would be more effective in treating some
patients than others.