 In the one-locus case, we saw that in a large randomly-mating population, there is a simple relationship between the gametic and zygotic frequencies. In the two-locus case, the same relationship holds. Thus for example, the frequency of the \(A_1 B_1 / A_1 B_1\) genotype will be \((x_1)^2\); the frequency of the \(A_1 B_1 / A_2 B_1\) genotype will be \(2x_1 x_3\), and so-on. (This can be established rigorously with an argument based on random sampling of gametes, just as in the one-locus case.) The first aspect of the Hardy-Weinberg principle—genotypic frequencies given by the square of the array of gametic frequencies—therefore transposes neatly to the two-locus case. However, the second aspect of Hardy-Weinberg—stable genotypic frequencies after one round of random mating—does not generally apply in the two-locus case.