1. Hardy-Weinberg Equilibrium Model

2. The Hardy-Weinberg model states that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors.

3. A population (or an allele) is not evolving if it is in Hardy-Weinberg equilibrium.

4. Conditions for an allele to be in Hardy-Weinberg equilibrium:
These conditions are impossible in nature!

5. We can compare a naturally occurring population to a theoretical population in Hardy-Weinberg equilibrium to see if the natural population is evolving.
A population is evolving if:
Theoretical population
In Hardy-Weinberg equilibrium
Naturally occurring population

6. How to calculate phenotypic frequency in a population:
3 white
5 black
8 total mice
f(white) =
f(black) = 3 8 5 8

7. How to calculate genotypic frequency in a population:
The frequency of the recessive genotype (we will call it aa) is the same as the frequency of the recessive phenotype.
f(white) =
f(aa) = 3 8 3 8

8. How to calculate genotypic frequency in a population:
The frequency of the heterozygous genotype (Aa) and the homozygous dominant genotype (AA) is harder to tell.
f(black) =
f(Aa) = ?
f(AA) = ? 5 8

9. The two Hardy-Weinberg formulae allow us to calculate allele frequency:
p2 + 2pq + q2 = 1
p + q = 1

10. The Hardy-Weinberg Variables:
p2 = f (AA) = f (homozygous dominant) 2pq = f (Aa) = f (heterozygote) q2 = f (aa) = f (homozygous recessive)
f (Aa)
Heterozygote
f (AA)
f (aa)
Homozyous dominant
Homozygous recessive
p2 + 2pq + q2 = 1

11. p = f (AA) = f (A) q = f (aa) = f (a)
p + q = 1

12. Using the Hardy-Weinberg equation to find f (AA), f (Aa) and f (aa):
Step 1: Find q2
Step 4: Find f (aa)
f (q2) = f (white) = = .36 3 8
f (aa) = f (q2) = .36
Step 2: Find q
Step 5: Find f (Aa)
f(q) = f (q2) = = .6
f (Aa) = 2pq = 2(.4)(.6) = .48
Step 3: Find p
Step 6: Find f (AA)
p + q = f (p) =
p = 1 – q f (p) = .4
f (AA) = f (p2) = .42 = .16