两对相对独立的等位基因控制两对相对性状,纯合子亲本杂交得到的F1自交后代有四种表现型,比例为9∶3∶3∶1,测交后代也有四种表现型,其比例为1∶1∶1∶1.但如果这两对等位基因控制同一性状或相互影响的话,F1自交后代的表现型和比例可能就会出现变形,就不是正常的完全显性的9∶3∶3∶1,测交后代比例也不是1∶1∶1∶1.下面就基因自由组合定律中9∶3∶3∶1的几种变式分析归纳如下. Two pairs of relatively independent alleles control two pairs of relative traits. There are four phenotypes of F1 selfing offspring obtained from the cross of homozygous parents, with a ratio of 9: 3: 3: 1 and also four phenotypes of tested offspring 1: 1: 1: 1. However, if the two pairs of alleles control the same trait or interact with each other, the phenotypes and proportions of the F1 selfing progeny may be distorted and not normal and completely dominant : 3: 3: 1, measured the proportion of offspring is not 1: 1: 1: 1. The following gene free association law 9: 3: 3: 1 variants of several variants are summarized below.