Hardy-Weinberg Equilibrium

Honors Biology

Is evolution occurring right now? How might a scientist

tell if evolution is occurring within a population?

Hardy-Weinberg Equilibrium Biologists use models to study populations Hardy-Weinberg equilibrium is a type of

model Provides a framework for understanding how

populations evolve

Hardy-Weinberg Equilibrium Conditions Genotype frequencies stay the same (no

microevolution) if all 5 conditions are met:1. Very large population size2. Isolation from other populations3. No Mutations4. Random Mating5. No natural selection

The Hardy-Weinberg Equation 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

Hardy-Weinberg Equation p + q = 1

p = frequency of dominant allele q = frequency of recessive allele

p2 + 2pq + q2 = 1 p2 = frequency of homozygous dominant genotype

(AA) 2pq = frequency of heterozygous genotype (Aa) q2 = frequency of homozygous recessive genotype

(aa)

Solve this story problem In pigs, the allele for black coat is

recessive to pink coats. B = pink; b = black Calculate q2 for the illustration shown

below. q2 = 0.25 (4/16)

Find q. q = 0.5

Find p. p = 0.5

Find 2pq. 2pq = 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? (q2) What percentage of the population is

heterozygous for this trait? (2pq) What percentage of the population is

homozygous white? (p2)