1. The Hardy-Weinberg Principle
By: Alex, Jared,
Merrick and Larisa

2. What Is It?
A principle that states in populations in which ONLY RANDOM CHANCE is at work, allele frequencies will remain constant generation to generation

3. The Hardy-Weinberg Equilibrium
1pp:2pq:1qq
This is the EXPECTED GENOTYPIC RATIO

4. Example- Blue Eyes & Brown Eyes
Say eye colour is inherited by dominance. B is the dominant allele for brown eyes and b is the recessive allele for blue eyes
“p” is the frequency of the B allele
“q” is the frequency of the b allele
So,
The genotype BB = pp
The genotype bb = qq
The genotype Bb = pq
According to the Hardy-Weinberg principle, the expected allele frequencies of this population should be 1pp: 2pq : 1qq generation after generation
For this example, this can also be written as 1BB: 2Bb: 1bb

5. So According To The Hardy-Weinberg Principle:
The genotypic ratio of this population should remain 1BB:2Bb:1bb generation after generation
But why isn’t this the case in nature?

6. BECAUSE
Any factor that causes allele frequencies to change leads to evolutionary change, and the Hardy-Weinberg principle does not apply

7. Therefore, It Only Applies If:
Mutation is not occurring
Natural selection is not occurring
The population is large (a smaller population increases chance of genetic drift)
All members of the population breed
All mating is totally random
Everyone produces the same number of offspring
There is no migration in or out of the population

8. Question Time 