1. KEY CONCEPT Hardy-Weinberg equilibrium provides a framework for understanding how populations evolve.

2. Hardy-Weinberg equilibrium describes populations that are not evolving. Biologists use models to study populations. Hardy-Weinberg equilibrium is a type of model.

3. Hardy-Weinberg equilibrium describes populations that are not evolving. Genotype frequencies stay the same if five conditions are met. –very large population: no genetic drift –no emigration or immigration: no gene flow –no mutations: no new alleles added to gene pool –random mating: no sexual selection –no natural selection: all traits aid equally in survival

4. Hardy-Weinberg equilibrium describes populations that are not evolving. Real populations rarely meet all five conditions. –Real population data is compared to a model. –Models are used to study how populations evolve.

5. Analyzing Gene Pools Gene pools are all alleles in a population (remember 1 individual has 2 alleles for each trait; EX: RR, Rr, or rr) p = frequency of dominant alleles = #R/total alleles q = frequency of recessive alleles = #r/total alleles p + q = 1 We can use the Hardy-Weinberg formula to calculate genotype frequencies: p 2 + 2pq + q 2 = 1 p 2 = RR 2pq = Rr q 2 = rr

6. Practicing H-W Equation 200 flower; red is dominant to white 143 flowers are red; 57 flowers are white Red Genotypes = RR or Rr White Genotype = rr Total alleles = 400 p 2 + 2pq + q 2 = 1 or RR + Rr + rR + rr = 1 q 2 (rr) = 57/200 = 0.285 q = √0.285 = 0.534 p + q = 1 therefore p = 1 – q = 1 – 0.534 = 0.466 p 2 (RR) = (0.466) 2 = 0.217 (0.217) + 2(0.466)(0.534) + (0.285) = 1 0.217 + 0.498 + 0.285 = 1 RR = 21.7%; Rr = 49.8%; rr = 28.5% therefore red = 71.5% & white = 28.5%