... gametes:¹

Think of drawing the Punnett square for a dihybrid cross, if you want.

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... disequilibrium.²

You will sometimes see $D$ referred to as the linkage disequilibrium, but that's misleading. Alleles at different loci may be non-randomly associated even when they are not linked.

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... gamete.³

We're assuming random union of gametes rather than random mating of genotypes.

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... frequency,⁴

The frequency of recombinant gametes in double heterozygotes.

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... frequency,⁵

The frequency of cytological crossover during meiosis.

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... population.⁶

Well, duh! Covariation of allele frequencies across populations means that alleles are non-randomly associated across populations. What other result could you possibly expect?

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