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
Microevolution
changes in gene pool over time
Gene pool
combination of all 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

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

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 skin is recessive to pink skin.
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)

10. Extra Help!
Bozeman Biology Solving Hardy Weinberg Problems