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 Equilibrium
Biologists use models to study populations
Hardy-Weinberg equilibrium is a type of model
Provides 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 size
Isolation from other populations
No Mutations
Random Mating
No natural selection

5. 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

6. 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)

7. 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)

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)