4. Population Genetics Gametic Phase Disequilibrium - Linkage Disequilibrium
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As we saw in the previous lecture, with a single autosomal locus, genotype frequencies in the ideal population reach equilibrium after one generation of random mating. In this video, I want to expand the Hardy-Weinberg analysis to consider a pair of loci simultaneously.
Within a given population, the non-random sharing of alleles at different loci in a gamete is called gametic phase disequilibrium, or misleadingly linkage disequilibrium.
Why the term linkage disequilibrium is misleading? The loci may be physically linked on the same chromosome or located on different chromosomes. In addition to the linkage, selection favoring one combination of alleles over another, genetic drift in a small population, and intermixture of populations with different allele frequencies can arise disequilibrium or in other words allelic association.
In this case, a specific allele at the first locus is associated with a specific allele at the second locus more often than expected by chance.