Population Genetics

• Population: group of individuals of the same species living in the same area at the same time which interbreed to produce viable offspring
• Population genetics: a study of genetic variability in pops and evolutionary forces
• Phenotypic: observable difference
• Mutation: heritable change seq = new allele
• Gene pool: all genes in a population
• Fixed allele: all individuals in gene pool are homozygous
• Allele Frequency: proportion of a specific allele in a particular pop
• Genetic equilibrium: allele freqs and genotype freqs do not change from gen to gen, pop not undergoing evolutionary change
• Hardy- Weinberg Equilibrium: The condition in which allele frequencies in a population do not change over time
• Five Conditions to maintain H-W: no mutation, random mating, no nat selection, very large pop size, no gene flow
• Mutation is raw material for natural selection, change in allele, change gene pool
• Mutation is rare so usually allele freq aren't changed especially in large populations
• non random mating: random mixing of gametes does not occur
• Natural selection is the only agent of mirco evoulution that is adaptive
• adaptive evolution: accumulates and maintains favorable genotypes
• Natural selection alters freq of heritable traits in three different ways: stabilizing, directional, and diversifying selection
• Stabilizing selection: favors and selects against extremes
• Directional selection: favors variant of one extreme
• Diversifying selection: Both extremes favored over average
• Genetic Drift: Random changes in small breeding population that decreases genetic variation due to allele loss
• genetic drift can alter allele freqs in a population
• Genetic drift has little effect on large population under most circumstances
• Founders effect: a few individuals colonize a new habitat and their gene pool has some of the original genes of the original population
• Bottleneck effect: size of a population is reduced by a sudden change in the environment
• Gene flow: movement of alleles between populations, usually due to migration or natural disasters