1. Hardy-Weinberg Equilibrium Honors Biology

2. Is evolution occurring right now?  How might a scientist tell if evolution is occurring within a population?

3. Hardy-Weinberg Theorem  Biologists use models to study populations  Hardy-Weinberg equilibrium is a type of model Provides a framework for understanding how populations evolve

4. The Hardy-Weinberg Theorem  Uses frequencies of alleles in a population’s gene pool to determine if (micro)evolution is occurring If allele frequencies change over time, the population is evolving If allele frequencies are stable, the population is at equilibrium

5. Hardy-Weinberg Equilibrium Conditions Genotype frequencies stay the same (no microevolution) if all 5 conditions are met: 1. Very large population size 2. Isolation from other populations 3. No Mutations 4. Random Mating 5. No natural selection

6. Hardy-Weinberg Equation  p + q = 1 p = frequency of dominant allele q = frequency of recessive allele  p 2 + 2pq + q 2 = 1 p 2 = frequency of homozygous dominant genotype (AA) 2pq = frequency of heterozygous genotype (Aa) q 2 = frequency of homozygous recessive genotype (aa)

7. Solve this story problem  In pigs, the allele for black skin is recessive to pink skin.  B = pink; b = black  Calculate q 2 for the illustration shown below.  q 2 = 0.25 (4/16)

8.  Find q. q = 0.5  Find p. p = 0.5  Find 2pq. 2pq = 0.5 This means 50% of the pink pigs are heterozygous.

9. Solve this story problem  In a certain flock of sheep, 4 percent of the population has black wool and 96 percent has white wool.  If black wool is a recessive trait: What percentage of the population is homozygous black? (q 2 ) What percentage of the population is heterozygous for this trait? (2pq) What percentage of the population is homozygous white? (p 2 )