Review for exam
one
The Scientific method
• Scientists use the Scientific Method to test
Theories.
– Generate an Observation
– Pose a Hypothesis
– Perform Experiments
– Analyze Results
– Reach a Conclusion--does the date support or
refute our Theory?
The Scientific method
• Scientists use the Scientific Method to test
Theories.
– Generate an Observation
– Pose a Hypothesis
– Perform Experiments
– Analyze Results
– Reach a Conclusion--does the date support or
refute our Theory?
Why do Experiments in Labs?
• Controls! Controls! Controls!
• Lab Experiments can prevent “variables”
– Variable: Factor that can cause observable change
and through results off.
• Independent – what you vary during the experiment.
Usually this will be time.
• Dependant – what you measure – what will change
during the experiment
– Control: Subject to all experimental steps EXCEPT
the experimental Factor.
Animalia – development by
means of an embryonic stage
No cell walls. Do not
undergo photosynthesis
Plantae – contain a cell wall
carry out photosynthesis
Non-motile life stages.
Fungi - contain cell wall
Do NOT photosynthesize
Protista – No cell walls
reproduce by spores – motile
Monera – the bacteria:
single-cell organisms
Box 6.2 (1)
Box 6.2 (2)
Components of a Cell
Components of a Cell
• Nucleus--contained within a cell by nuclear
envelope. The nucleus contains DNA.
• Ribosomes--these structures make protein.
• Endoplasmic Reticulum--this is a membrane
network composed RER--rough has ribosomes
makes proteins, and SER--smooth makes lipids.
• Golgi Apparatus--modifies proteins involved in
secretion.
• Endomembrane system--Composed of nuclear
envelope, ER, Golgi, Lysosomes and Vesicles, these
organelles all work together to make protein sorting
and protein secretion possible.
The Mitochondria
• Contain their own DNA and
protein-synthesizing machinery
– Ribosomes, transfer RNAs,
nucleotides.
– Thought to have evolved
from endosymbiotic bacteria.
– Divide by fusion
– The DNA is in the form of
circular chromosomes, like
bacteria
– DNA replication is
independent from DNA
replication in the nucleus
The Mitochondria
Site of Cellular Respiration
• This process requires oxygen.
• Composed of three stages:
– Glycolysis--glucose splitting,
occurs in the cell. Glucose is
converted to Pyruvate.
– Krebs cycle--Electrons are
removed--carriers are
charged and CO2 is
produced. This occurs in the
mitochondrion.
– Electron transport--electrons
are transferred to oxygen.
This produces H2O and ATP.
Occurs in the mito.
The Chloroplast
• Contain their own DNA and
protein-synthesizing machinery
– Ribosomes, transfer RNAs,
nucleotides.
– Thought to have evolved
from endosymbiotic bacteria.
– Divide by fusion
– The DNA is in the form of
circular chromosomes, like
bacteria
– DNA replication is
independent from DNA
replication in the nucleus
The Chloroplast
• Membranes contain chlophyll
and it’s associated proteins
– Site of photosynthesis
• Have inner & outer membranes
• 3rd membrane system
– Thylakoids
• Stack of Thylakoids = Granum
• Surrounded by Stroma
– Works like mitochondria
• During photosynthesis, ATP
from stroma provide the energy
for the production of sugar
molecules
Terms:
• Phenotype
– An organism’s physical traits
• Genotype
– An organism’s genetic makeup
Allele
• Allele: Alternate form of a gene at same
position on pair of chromosomes that affect the
same trait.
• Dominant Allele: Capital Letter--O
• Recessive Allele: lowercase letter--o
• Homozygous Dominant--OO
• Homozygous Recessive--oo
• Heterozygous--Oo
Stages of Division
• Prophase--nuclear envelope breakdown,
chromosome condensation, spindle formation.
• Metaphase--chromosomes are lined up
precisely on the metaphase plate, or middle of
the cell.
• Anaphase--spindle pulls sister chromatids
apart.
• Telophase--chromatids begin to decondense
and become chromatin. Spindle disappears.
• Cytokinesis--divide cell and organelles. Actin
ring, or cleavage furrow splits cell.
Review: Comparing Mitosis and Meiosis
Mitosis
Meiosis
Parent cell
(before chromosome duplication)
Duplicated chromosome
(two sister
chromatids)
Site of
crossing over
Chromosome
duplication
Chromosome
duplication
Tetrad formed
by pairing of
homologous
chromosomes
Pairing of
homologous
chromosomes
2n = 4
Prophase
Chromosomes
align at the
middle of
the cell
Metaphase
Anaphase
Telophase
2n
Sister
chromatids
separate
during anaphase
Daughter cells
of mitosis
2n
Prophase I
Tetrads
align at the
middle of
the cell
Homologous
chromosomes
separate
during
anaphase
I; sister
chromatids
remain
together
No further
chromosomal
duplication;
sister
chromatids
separate
during
anaphase II
Meiosis I
Metaphase I
Anaphase I
Telophase I
Daughter
cells of
meiosis I
Haploid
n=2
Meiosis II
n
n
n
n
Daughter cells of meiosis II
Prophase -I
Replicated pairs of chromosomes
line up side by side.
These pairs are called Homologous-both have same gene order (gene
for eye color, hair color, etc).
Sister chromatid from one pair
interact with a Sister chromatid from
another pair.
One sister is from father, one sister
from mother, but they have same
gene order.
Prophase -I
• This interaction is called
Synapsis.
• Synapsis results in the
formation of a Tetrad
(4
sisters together).
• Crossing over swaps
sections of homologous
genes.
•Meiosis I
Meiosis I: Homologous
chromosomes separate
Prophase I
Sites of crossing over
Metaphase I
Microtubules attached
to Chromosomes
Anaphase I
Sister chromatids
remain attached
Telophase I
and Cytokinesis
Cleavage
furrow
Spindle
Sister
chromatids
Tetrad
Homologous
chromosomes
pair and exchange
segments
Centromere
Tetrads line up
Pairs of homologous
chromosomes
split up
Two haploid cells
form: chromosomes
are still double
•Meiosis II
Meiosis II:
Sister chromatids separate
Prophase II
Metaphase II
Anaphase II
Telophase II
and Cytokinesis
Sister chromatids
separate
Haploid daughter cells
forming
During another round of cell division, the sister chromatids finally separate;
four haploid daughter cells result, containing single chromosomes
Sex Determination
• All embryos start on a neutral or
"indifferent" path. The 4 week old
embryo is indifferent
• By 7 weeks, the SRY (sex-related)
gene encoded by the short arm of
the Y chromosome begins to roar!
• Testis determining factor converts
progesterone to testosterone
Sex Determination
• Indifferent embryos have two sets of
ducts:
• Müllerian ducts--will be come the
future oviducts--thus female.
•
Wolfian ducts--will become the
future vas deferens--thus male
– dependent on testosterone for its
continued development
• The testes also produce an antiMüllerian hormone that promotes
regression of the Müllerian ducts
– without SRY, the indifferent embryo
will naturally develop into a female
Mutations
Figure 3.6a
Mutations
Sex Chromosomal Disorders
• Turner Syndrome – XO only one sex
chromosome
• Short, thick neck and stature
• Do not undergo puberty, or menstruate,
• no breast development
• Kleinfelter Syndrome – XXY
•
•
•
•
•
Testis and prostate underdeveloped
No facial hair
Brest development
Long arms and legs: big hands and feet
Can be mentally retarded
An XY Individual with Androgen
Insensitivity Syndrome
Androgen Insensitivity Syndrome is a sex reversal condition where XY
individuals look female. These individuals have the Y chromosome and
functional SRY. These individuals have testis which generate AMH and
testosterone. However, the genetic mutation results in a lack of the
testosterone receptor. Estrogens are made in the adrenal gland which drive
phenotypic development. As adults, these individuals have testes in the
abdomen and lack a uterus and oviducts.
DNA Replication
• Each new double helix is composed of an old
(parental) strand and a new (daughter) strand.
• As each strand acts as a template, process is called
Semi-conservative Replication.
• Replication errors can occur. Cell has repair
enzymes that usually fix problem. An error that
persists is a mutation.
• This is permanent, and alters the phenotype.
The structure of RNA
• Formed from 4
nucleotides, 5 carbon
sugar, phosphate.
• Uracil is used in RNA.
– It replaces Thymine
• The 5 carbon sugar has
an extra oxygen.
• RNA is single stranded.
Central Dogma of Molecular
Biology
• DNA holds the code
• DNA makes RNA
• RNA makes Protein
• DNA to DNA is called
REPLICATION
• DNA to RNA is called
TRANSCRIPTION
• RNA to Protein is called
TRANSLATION
Genes can lead to inherited
diseases
• A gene which doesn’t function on an autosomal
chromosome can lead to devastating diseases
• Autosomal chromosomes are 22 pairs of
chromosomes which do not determine gender
• Such diseases can be caused by both a dominant or a
recessive trait
Autosomal Recessive Disorders
• Tay-Sachs Disease:
– Jewish people in USA (E. Euro descent)
– Not apparent at birth
– 4 to 8 months
• Neurological impairment evident
• Gradually becomes blind and helpless
• Develops uncontrollable seizures/paralyzed
• Allele is on Chromosome 15
– Lack of enzyme hexosaminidase A (Hex A)
• Lysosomes don’t work, build up in brain
Autosomal Recessive Disorders
• Cystic Fibrosis
– Most common in USA (Caucasian)
– 1 in 20 caucasians is a carrier
– Mucus in bronchial and pancreas thick/viscous
– Breathing and food digestion problems
• Allele is on chromosome 7
– Cl ions can not pass through plasma membrane
channels
• Cl ions pass –water goes with it. No water, thick
mucus
Autosomal Recessive Disorders
• Phenylketonuria (PKU)
– Affects in in 5,000 newborns
– Most common nervous system disorder
• Allele is on chromosome 12
– Lack the enzyme needed for the metabolism of the
amino acid phenylalanine
– A build up of abnormal breakdown pathway
• Phenylketone
• Accumulates in urine. If diet is not checked, can lead
to severe mental retardation
Autosomal Dominant Disorders
•
•
•
•
•
Neurofibromatosis
Very common genetic disorder
Tan spots on skin
Later tumors develop
some sufferers have large head and ear and eye
tumors.
• Allele is on chromosome 17
– Gene controls the production of a protein called
neurofibromin
– This naturally stops cell growth
Autosomal Dominant Disorders
•
•
•
•
•
Huntington Disease
Leads to degeneration of brain cells
Severe muscle spasms and personality disorders
Attacks in middle age
Allele is on chromosome 4
– Gene controls the production of a protein called
huntington
– Too much AA glutamine. Changes size and shape of
neurons
GOOD LUCK
NEXT WEEK!