1. Study of changes in gene
frequencies of population
2. Gene frequency- relative
occurrence of gene’s alleles
in population
Population Genetics
3. Models- Allele frequencies,
genealogical, deterministic, &
stochastic
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Population Genetics: Understanding Gene Frequencies and Evolution - Prof. Roman E. Boldyre, Study notes of Ecology and Environment
An overview of population genetics, focusing on gene frequencies, models, and the hardy-weinberg equilibrium. Topics include allele frequencies, deterministic and stochastic theories, and the impact of natural selection, genetic drift, and mutation on genetic equilibrium.
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Pre 2010
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- Study of changes in gene frequencies of population
- Gene frequency- relative occurrence of gene’s alleles in population
Population Genetics
- Models- Allele frequencies, genealogical, deterministic, & stochastic
- Classical population genetics 2. Based on Mendel’s principles of complete dominance, segregation, & independent assortment
Theory of Allele Frequencies
- Predictable
- Assumes allele frequencies = expected frequencies
Deterministic Theory
- True if population sizes are infinite
- Less predictable, more probabilistic
- Allows for variance around expected frequencies
Stochastic Theory
Population Estimation
N = population =?
nm = sample captured, marked, & released nr = sample recaptured
nrm = sample recaptured & marked
- Genetic equilibrium- frequency of alleles in population stays same unless acted on by some factor
- Conditions- population must be large & randomly mating with no natural selection, gene flow or mutation
Hardy-Weinberg Equilibrium
Given P + p = 1 Let P = freq of nonPKU allele p = freq of PKU allele Given P^2 + 2Pp + p^2 = 1 Let P^2 = PP = freq of homozygous nonPKU ind 2Pp = freq of heterozygous nonPKU ind p^2 = pp = freq of homozygous PKU ind
Hardy-Weinberg Example
If freq of homozygous PKU ind = 0.0001, then
% homozygous PKU ind = 0.01%
% homozygous PKU individuals
2Pp = 2 ( 0.99 x 0.01) 2Pp = 0.
If freq of heterozygous nonPKU ind = 0.0198 , then
% heterozygous nonPKU ind = 1.98%
% heterozygous nonPKU individuals
- Natural Selection
- Migration
- Genetic Drift
- Isolation
- Mutation
- Meiotic Drive
Changes in Genetic Equilibrium
Time 1
Directional Selection
Time 2
Directional Selection
Time 2
Stabilizing Selection
Time 1