Free Hardy-Weinberg OCR A Level Biology revision notes – covering specification point 6.1.2(f).
The proportion of genotypes in a population can be calculated using the Hardy–Weinberg equation.
The Hardy–Weinberg principle predicts expected genotype frequencies within a non-evolving population (allele frequencies do not change across generations).
The Hardy-Weinberg equation is:
p + q = 1
p² + 2pq + q² = 1
Where:
- p = frequency of the dominant allele (A)
- q = frequency of the recessive allele (a)
- p² = homozygous dominant (AA)
- 2pq = heterozygous (Aa)
- q² = homozygous recessive (aa)
Because p + q = 1, knowing one allele, or genotype, frequency allows the rest to be calculated.