Genetics exam 1
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Genetics exam 1
Genetics exam 1, ch 1, 2, 3
the study of all aspects of genes (cell, organism, population)
fundamental units of biological information
composed of DNA
the study of the molecular processes underlying gene structure and function
discovery of DNA allowed this to exist.
What kind of information is held within cells that allows them to rebuild an entire complex adult organism?
DNA lies within chromosomes within nucleus of every cell, passed from generation to generation through nuclear divisions (meiosis and mitosis)
What constitutes biological information?
Life regenerates every generation from single cells
study of complete gene sets (genomes).
James Watson and Francis Crick
1953, solved structure of DNA (double helix)
Inferred that DNA has info written in genetic code (4 nucleotides) which passes from generation to generation.
organism's complete set of genetic information
linear series of 4 molecular building blocks (nucleotides)
passes from generation to generation
inferred by Watson and Crick
2 identical chromosome sets/copies of genome (pairs of homologous chromosomes or homologs)
or homologs, 2 copies of same chromosome, as seen in diploid organism
number of chromosomes in basic set.
Only one copy of each gene.
Human sex cells (n=23)
chromosomes consist of:
DNA (~1m) wrapped around histone protein until 4cm "supercoil"
Centromere and telomeres of chromosome, tightly wrapped so less gene expression
tips of chromosome
made of heterochromatin
center of chromosome, made of heterochromatin
"legs" of X chromosome, cross of X and tips are heterochromatin
More loosely wrapped, more expressed
main element of form in organisms (structural, enzymatic, regulatory)
3 types of proteins
structural - keratin
enzymatic - amylase, polymerase
regulatory - turns on and off to regulate expression
Main task of living system
convert info of DNA into proteins
process and "language" is same in all organisms
The Central Dogma
DNA --(transcription)--> RNA --(translation)--> Protein
DNA to RNA, occurs in nucleus
mRNA to Ribosomes, occurs in cytoplasm/ER
the way life perpetuates over time, producing new organisms and regenerating new organisms from single progenitor cell
complete study of all proteins
complete study of neuron connections
not very expressed chromosome
get cut out of gene in replication
stay in in gene replication
Only have one, everything is required. Also have plasmids floating in cell, not required but specialized, passed. Extrachromosomal
extrachromosomal DNA floating in cell, not required but specialized and passed
NOT ALWAYS DNA, only thing that can use RNA instead, not alive because cannot procreate alone.
process and language pretty much same in all organisms. Evolutionarily as good as it gets.
If mammal and fish are the same, pretty good bet.
free ribosome proteins
make cytoplasmic proteins that work inside the cell
post-meiosis, each daughter chromosome has 1 old and 1 new strand.
every cell that isn't a sex cell.
shape physical structure of genome. Has to do with loosely or tightly wrapped, making transcription possible or impossible. "switched on" or "switched off"
NON-ALLELIC, heritable but not based on mutations in DNA
silent (condensed) chromatin
methylated cytosines (red circles)
active, open chromatin
unmethylated cytosines (white circles)
the process whereby individuals with a particular characteristic may reproduce better than others in a given environment.
Make more offspring, more people with trait
similarity due to shared ancestry due to common ancestor
Theory of Evolution
notion of natural selection acting on variation.
Change in DNA generates variation, which is raw material for evolution
phylogenic tree showing how far apart or close species are genetically and where they branched.
shows descent of various species through ancestral forms over time
Differences in DNA sequences are quantified and species with similar sequences are placed closer together
used to test patterns of evolutionary relationships previously proposed exclusively in physical homology
altered form of normal property
crops modified for insecticide and herbicide resistance
goats produce anti-blood-clotting protein antithrombin and secrete it in milk
bacteria synthesize important drugs like human insulin and growth hormone
yeast for bread/wine
How do geneticists analyze biological properties?
to find the subset of genes in the genome that influence the property (gene discovery)
Detection of single-gene inhertiance patterns
1)mate a wild type and a mutant
2) mate their progeny
the ratio fo mutant to wt will reveal if the difference is held in a single gene
Father of Genetics
Garden Pea (psium sativum) (shape/color of pea, of pod, color of flower, plant height, position of flower).
studied contrasting phenotypes
Breeding with self, pollenate stigma with own pollen
Opposite of cross-pollination
first filial generation
Law of Equal Segregation
Genes come in two forms, called alleles
Meiosis, gene pair separate EQUALLY into eggs or sperm
One gamete has only one copy of gene
A pair of identical alleles
pair of different alleles
VISIBLE characteristic (3:1)
GENETIC characteristic, 1:2:1
What are alleles at molecular level
different variations of same gene. Can be mutation.
Why are alleles with mutation normally recessive?
Bad for species
at centromere on chromosome
between homologous chromosomes, holds together
gene does not work, mutation likely at active site (or promoter)
gene is active but not great, semi-functional.
Mutation likely at end, or on edge of active site
primary phenotype of a gene
protein it produces (and functional differences)
Defective allele of phenylananine hydroxylase (PAH), doesn't turn phenylalanine into tyrosine, instead gets turned into phenylpyruvic acid, which cause neuronal degeneration/lack of development.
SO MANY MUTANT SITES in PKU GENE
mutation at very end, not on active site. Gene functions normally
one copy is enough to have wild type phenotype
single wild type allele does not provide normal function
human # of chromosomes (autosomal and sex)
22 homologous pairs of autosomes + 2 sex chromosomes
Telomere areas of sex chromosomes are called
pseudoautosomal region 1 and 2, on either side of the differential region
Thomas Hunt Morgan
worked with Drosophilia eye color. Reciprocal crosses did not make same phenotypic ratios
proved existance of chromosomes and that genes are on them "the chromosome theory of inheritence
chromosomal theory of inheritance
Thomas Hunt Morgan and Drosophilia
member of family who first comes to attention of geneticist (person requesting info, usually)
autosomal recessive disorders
progeny of unaffected parents
affected progeny include both male and female
pedigree looks bare, few affected
autosomal dominant disorders
phenotype appears in every generation of pedigree
affected parents transmit to offspring of both genders
Ability to taste PTC (Phenylthiocarbamide)
Dominant taste allele, dimorphism
in population, polymorphism is coexistance of two or more common phenotypes of a character (eye color, hair color, chin dimple, widow's peak, earlobes, etc). Dominant is written first.
X-linked recessive disorders
many more males than females affected
none of offspring of affected male show the phenotype but all daughters are carriers
no sons of affected male show phenotype and cannot pass condition on
(red-green color blind, hemophilia)
affected males pass to all daughters but no sons
affected (heterozygous) females married to unaffected males pass to half of sons and daughters
fathers pass to sons
no cases of nonsexual phenotypic variants associated with Y
the probability of two independant events both occurring is the product of their individual probabilities
probabilities of either of two mutually exclusive events occurring is the sum of their individual probabilities
(Roll 2 4s OR 2 5s. 1/36 + 1/36 = 1/18)
belief that you are the only one who doesn't understand, prevalent in large groups
Two genes on different chromosomes will act independantly at meiosis
on same chromosome, will always match up
on different chromosomes, will assort independantly.
analysis of one gene
analysis includes 2 genes
semicolon indicates different chromosomes (A/a;B/b)
analysis includes 3 genes
semicolon indicates different chromosomes (A/a;B/b)
result of 2 hets, dihybrid cross. Creates 2 3:1 ratios in phenotypes
used instead of punnet square in dihybrid cross, punnet is too hard
Heteromorphic chromosomes, one had a truncated end so could tell apart. Also had single chromosome (grasshopper). Found 50% ratio, proved INDEPENDANT ASSORTMENT
Which meiotic stage generates mendel's second law?
Anaphase (independant assortment)
cross with recessive to determine genotype of unknown
The F1 heterozygote hybrid shows greater size and vigor than contributing lines
can't make itself, have to keep crossbreeding parents
A group of non-allelic genes that, together, influence a phenotypic trait.
non-alleleic, more than one gene that come together to influence one trait, also includes environmental factors.
Why are mitochondria and chloroplasts special?
Have own DNA (nucleoids), not associated with (histone) proteins. Not functionally autonomous, but make ATP
Uniparental inheritance (ONLY MOM)
Mitochondrial DNA, can be mutant and cause phenotypic variants. No histone proteins, very small
The number that determines if something is significant or insignificant (5% in chi square test). If greater than 5%, non-significant.
used to compare data with expected results, quantifies acceptable deviation.
Reject hypothesis with less than 5% (p-value)(numbers to the right)
df = phenotypes you can see -1