2 Is evolution occurring right now? How might a scientist tell if evolution is occurring within a population?
3 Hardy-Weinberg Equilibrium Biologists use models to study populationsHardy-Weinberg equilibrium is a type of modelProvides a framework for understanding how populations evolve
4 Hardy-Weinberg Equilibrium Conditions Genotype frequencies stay the same (no microevolution) if all 5 conditions are met:Very large population sizeIsolation from other populationsNo MutationsRandom MatingNo natural selection
5 The Hardy-Weinberg Equation Uses frequencies of alleles in a population’s gene pool to determine if (micro)evolution is occurringIf allele frequencies change over time, the population is evolvingIf allele frequencies are stable, the population is at equilibrium
6 Hardy-Weinberg Equation p + q = 1p = frequency of dominant alleleq = frequency of recessive allelep2 + 2pq + q2 = 1p2 = frequency of homozygous dominant genotype (AA)2pq = frequency of heterozygous genotype (Aa)q2 = frequency of homozygous recessive genotype (aa)
7 Solve this story problem In pigs, the allele for black coat is recessive to pink coats.B = pink; b = blackCalculate q2 for the illustration shown below.q2 = 0.25 (4/16)
8 Find q. Find p. Find 2pq. q = 0.5 p = 0.5 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? (q2)What percentage of the population is heterozygous for this trait? (2pq)What percentage of the population is homozygous white? (p2)