The document discusses the Hardy-Weinberg principle of population genetics. It states that the frequency of alleles in a population will remain constant over generations if the population is large, randomly mating, and not subject to mutations, gene flow, or selection pressures. It provides an example using cat coat color alleles to demonstrate calculating genotype frequencies based on observed phenotypes and applying the Hardy-Weinberg equations. Factors that can disrupt Hardy-Weinberg equilibrium and cause allele frequencies to change are also noted, including mutation, migration, natural selection, and genetic drift.

1. Population Genetics The Hardy-Weinberg principle Factors that can change allele frequencies

2. A. The Hardy-Weinberg Principle The frequency of an allele in a population will remain constant over time, provided that the following conditions are met: The population is large and randomly breeding There are no conditions acting on the population to change the allele frequency

3. A. The Hardy-Weinberg Principle Consider a gene that has two alleles, A and a Let p = the frequency of A (in a population) q = the frequency of a The frequency of AA = p 2 The frequency of aa = q 2 The frequency of Aa = 2 pq p 2 + 2 pq + q 2 = 1

4. Hardy-Weinberg Principle Population genetics - study of properties of genes in populations blending inheritance phenotypically intermediate (phenotypic inheritance) was widely accepted new genetic variants would quickly be diluted

5. Hardy-Weinberg Principle Hardy-Weinberg - original proportions of genotypes in a population will remain constant from generation to generation Sexual reproduction (meiosis and fertilization) alone will not change allelic (genotypic) proportions.

6. Hardy-Weinberg Equilibrium Population of cats n=100 16 white and 84 black bb = white B_ = black Can we figure out the allelic frequencies of individuals BB and Bb?

7. Hardy-Weinberg Principle Necessary assumptions Allelic frequencies would remain constant if… population size is very large random mating no mutation no gene input from external sources no selection occurring

8. Hardy-Weinberg Principle Calculate genotype frequencies with a binomial expansion (p+q) 2 = p 2 + 2pq + q 2 p2 = individuals homozygous for first allele 2pq = individuals heterozygous for alleles q2 = individuals homozygous for second allele

9. p 2 + 2pq + q 2 and p+q = 1 (always two alleles) 16 cats white = 16bb then ( q 2 = 0.16 ) This we know we can see and count!!!!! If p + q = 1 then we can calculate p from q 2 Q = square root of q 2 = q √.16 q=0.4 p + q = 1 then p = .6 (.6 +.4 = 1) P 2 = .36 All we need now are those that are heterozygous (2pq) (2 x .6 x .4)= 0.48 .36 + .48 + .16 Hardy-Weinberg Principle

10. Hardy-Weinberg Equilibrium

11. B. Factors That Change Allele Frequencies Mutation Migration Natural selection Random genetic drift