Many traits in populations are well understood as being Mendelian effects at single loci or additive polygenic effects across numerous loci. However, there are important phenomena and traits that are intermediate between these two extremes and are known as oligogenic traits. Here we investigate digenic, or two-locus, traits and how their frequencies in populations are affected by non-random mating, specifically inbreeding, linkage disequilibrium, and selection. These effects are examined both separately and in combination to demonstrate how many digenic traits, especially double homozygous ones, can show significant, sometimes unexpected, changes in population frequency with inbreeding, linkage, and linkage disequilibrium. The effects of selection on deleterious digenic traits are also detailed. These results are applied to both digenic traits of medical significance as well as measuring inbreeding in natural populations.

群体中的许多性状被充分理解为单个基因座的孟德尔效应或多个基因座的加性多基因效应。然而，有一些重要的现象和性状介于这两个极端之间，被称为寡基因性状。在这里，我们研究双基因或双基因座性状，以及它们在群体中的频率如何受到非随机交配，特别是近交、连锁不平衡和选择的影响。对这些效应进行单独和组合检查，以证明有多少双基因性状，尤其是双纯合性状，可以通过近交、连锁和连锁不平衡表现出群体频率的显着（有时是意想不到的）变化。还详细介绍了选择对有害双基因性状的影响。