eli5 : What is the Hardy Weinberg Equation and how does it apply to DNA test?
In: Biology
It’s basically an equation to tell you the frequencies of specific genotypes in a population. In the equation:
p^2 + 2pq + q^2
the p is the frequency of the dominant A allele and the q is the frequency of the recessive “a” allele. So, the p^2 term is the frequency of the AA genotype, the q^2 term is the frequency of the aa genotype, and the middle term is the frequency of the Aa genotype.
Note that p and q MUST add to 1. It wouldn’t really make sense to have 30% of the alleles be an A and 80% of them be an “a” because then we’d be accounting for 110% of the alleles (which is impossible). We also know that the original equation, p^2 + 2pq + q^2 must also add up to 1 for the same reasons.
Now, why is this useful? If you think about it, the equation allows you to find the frequency of an allele from a variety of different pieces of information. If I know the frequency of the “aa” genotype (let’s say it’s 0.16), I know that the q^2 term is going to be 0.16. I can take the square root of this to get q, the frequency of the a allele. I can use this information and the fact that p+q=1 to find the p value, and therefore solve the Hardy Weinberg equation and find all of the genotype frequencies.
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