Linkage disequilibrium

Linkage disequilibrium is the non-random association of alleles at different loci, not necessarily on the same chromosome, in a population. Linkage disequilibrium describes a situation where some combinations of alleles or genetic markers appear more or less frequently than would be expected from a random formation of haplotypes from alleles based on their frequencies. The degree of linkage disequilibrium is measured as the difference between observed and expected (assuming random distributions) allelic frequencies.