heterozygote advantage

Hedrick PW 2012 What is the evidence for heterozygote advantage selection? TREE 27:698-704.

• loci with heterozygote advantage must be considered only a small minority of all loci in a species

• it is generally not possible to distinguish between loci experiencing balancing selection or positive selection in the form of incomplete selective sweeps using a signal of extended linkage disequilibrium
• using a test based on a combination of excess variation in the region linked to the putative selected locus and intermediate frequency of alleles at the locus, 60 of 13 400 genes in humans – only 0.45% – showed signals of balancing selection

• a recent theoretical treatment [32] suggested that a high rate of adaptation in diploids might result in extensive short-lived balancing selection, primarily heterozygote advantage
• there does not appear to be any evidence supporting this view beyond the data presented here