HardyWeinberg Equilibrium Honors Biology Is evolution occurring right

Hardy-Weinberg Equilibrium Honors Biology

Is evolution occurring right now? • How might a scientist tell if evolution is occurring within a population?

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

The Hardy-Weinberg Theorem Microevolution • ■ changes • in gene pool over time Gene pool ■ combination • • of alleles for a trait in a population If allele frequencies change over time, the population is evolving If allele frequencies are stable (don’t change), the population is at equilibrium and no evolution is occurring

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

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

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)

• Find q. ■ • Find p. ■ • q = 0. 5 p = 0. 5 Find 2 pq. ■ ■ 2 pq = 0. 5 This means 50% of the pink pigs are heterozygous.

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? (2 pq) What percentage of the population is homozygous white? (p 2)

Extra Help! • Bozeman Biology Solving Hardy Weinberg Problems