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Hardy-Weinberg

In a large population where mating is random and there is no selection, migration or mutation that matters, the allele frequencies stay put. If we call the frequency of a by q and of A by p, then p plus q equals 1. The share that shows a recessive trait is q squared. The share of carriers, Aa, is 2pq. The formula is used to estimate how many carry a hidden allele when you only see the recessive individuals. It is a model. Real populations often break the assumptions a little.

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Example

1% have genotype aa, so $q^2 = 0.01$, $q = 0.1$ and $p = 1 - 0.1 = 0.9$.

Carriers: $2 \cdot 0.9 \cdot 0.1 \cdot 100 = 18$%.

← A cross of Aa with aa · Energy in the food chain →

Part of Biology 1: Heredity and genetics.