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31 Cards in this Set

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What are the postulates of natural selection?
Variability, Heritability, Variation in reproductive success, Survival/repro is non-random
What did the pea aphid and desert locust examples illustrate?
Evironmental conditions inducing variability in phenotypes that IS NOT heritable.
What does a heritability score of 1 mean?
A strong parent-offspring correlation. What does it come from?
The slope of the regression line is 1. Mean parental value trait of parent (x axis) against mean value of phenotype in all of the parents' offspring.
Chromosome definition
allele definition
one of two or more forms of a gene or a genetic locus;
Alternate form of a gene
genome definition
the entirety of an organism's hereditary information
-made of DNA or RNA
genetic code
haploid number
A and G
C and T
a long, continuous, and unbranched peptide. Peptides are...
What are sources of genetic variation?
A. Mutation
b. Independent assortment
c. Recombination
Transition versus transversion
Types of mutations
-Transitions happen more commonly; less disruptive to DNA replication/protein (A to G; C to T)
-Transversions are a purine to pyrimidine change (A to C; G to T)
this actually isn't as intuitive as I thought. make sure you know.
Common cause of variability at microsatellites?
Replication slippage
Large scale mutation examples
-Unequal crossing-over (non-homologous recombination
-Inversions; double stranded breaks
-Translocations among chromosomes
Hardy-Weinberg principle
-Null model
-What to expect if evolution isn't happening
-No change in allele frequencies between generations
-HW proportions are restored in a single generation of random mating
Assumptions of HW principle
-No selection
-No migration
-No mutation
-Large pop size
-Random mating (panmixia)
What are the four evolutionary "forces"?
Selection, drift, mutation, migration
Relative fitness
Fitness of genotypes relative to a reference genotype
1 = maximal fitness
Selection coefficient
s = 1 - w
Also represents fitness of genotypes. When no selection against a genotype, w = ___ and s=_____. When genotype is lethal, w=____ and s=_____
1, 0
When selection is for recessive and against a dominant allele...
Evolution is slow to remove A at first b/c a is hiding in heterozygotes. Removal of A accelerates towards the end.
When selection is for a dominant and against a recessive allele...
a will be removed quickly at first, then slower toward the end. This is because some a alleles are hiding in heterozygotes.
Selection favoring heterozygotes...
-is termed overdominance
-maintains diversity because one allele will never be fixed (none lost if heteros are favored)
-Pop will always evolve to a stable equilibrium maintaining both alleles
Freq-dependent selection...
-maintains diversity in a population
-e.g. rare prey morph undetected by predator; higher fitness until it becomes the common morph; predator learns this new common morph which becomes selected against (decreasing fitness); original common morph re-emerges, driving pop back to equilibrium
-Is weak (slow) evo force
-Can change allele freqs, but over long periods of time
-Does not typically change HWP much
-Is the ultimate source of genetic variation
Hardy-Weinberg take-homes
1. It's possible to change gt freqs without change in allele freqs
2. HW equil does NOT mean p=0.5 and q-0.5
3. Deviation from HWP is a weak test of evolution
-Lack of deviation doesn't necessarily mean no evolution
-Conversely, if there is deviation, good chance that something interesting is going on.
4. HWP proportions will be restored in a single generation of random mating! So it can be used to calculate next generation gt freqs after selection, migration, etc.
Selection take-homes
Mutation take-homes
A "weak" force in terms of rate of evolution, but...
the ULTIMATE source of variation: without new mutations, evo can eventually grind to a halt. Lack of variation = no evolution.
Migration (aka "________") is...
"gene flow"
Movement of alleles between populations