Genetics exam 1
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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)
- humans 2n=46
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)
- deacetylated histones
- active, open chromatin
- unmethylated cytosines (white circles)
- acetylated histones
- 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
- gene therapy
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
- 1860, Czech
- 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
- Mendel's 1st
- 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)
- 46 chromosomes
- 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
- early 1900s
- 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
- sex-linked inheritance
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)
- Very rare
- affected males pass to all daughters but no sons
- affected (heterozygous) females married to unaffected males pass to half of sons and daughters
- (Hypophospahtemia, hypertrichosis)
- fathers pass to sons
- no cases of nonsexual phenotypic variants associated with Y
- (Hairy ears)
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
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