Evolution Exam 2

genetic variation

some individual variation is explained by the effect of genes (single genes vs many genes)

environmental variation

some individual is explained by the effects of environment (ex. presence of predators)

genotype by environment interaction

individual variation can be explained by interactions between genotype and environment (temperature dependent sex determination)

population-genetic

change in the genotype frequencies over generations within populations

locus (pl. loci)

a location on the chromosome where a gene or other dna interval is combined

genes

sequences that are transcribed (DNA -> mRNA)

protein-coding

genes that are translated (mRNA -> amino acid)

alleles

different variants of the gene that occur at each locus

genotype

sequence of alleles

Hardy-Weinburg equilibrium

null model for population genetics
Assumptions: no selection, no mutations, no migration, no genetic drift, random mating occurs

How to test HWE?

1. calculate genotype frequencies in current population
2. calculate allele freqiencies in current population
3. predict genotype frequencies in next generation
4. compare predicted to observed genotype frequincies

Law of segregation

2 alleles at each locus are seperated at meiosis, only one (randomly chosen) allele per gamete

non-random mating

most animals have inbreeding avoidance
with each generation, more heterozygotes are lost

Inbreeding coefficient

F=0 -> no inbreeding
F more than 0 -> inbreeding

mutation

source of new genetic variation
change in nucleotide sequence, gene duplication, change in chromosome sequence, whole genome duplication

nonsense mutation

mutation that changes the encoded amino acid to stop codon

nonsynonymous mutation

mutation that changes the identity of an amino acid (replacement)

synonymous mutation

mutation that does not change the amino acid (silent)

continent-island model

assume one-way movement from large population on continent to small population on island
equilibrium: p=pm
after enough time, allele frequency on the island will be the same as it is on the continent

affects of gene flow between populations

increases in allelic diversity within populations
homogenization of allele frequencies between populations

Fst

measures gene flow by variance in allele frequencies
F = 0 = lots of gene flow
F = 1 = no gene flow
populations close together have lots of gene flow = low Fst
populations further apart have less gene flow = high Fst