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独立遗传的两对相对性状的纯合亲本杂交,杂交后代一般会表现出9:3:3:1的性状分离比,即孟德尔比率。但有许多遗传实例却偏离了这个比率,本文对此作一探讨。1 孟德尔比率出现的条件(1)亲本必须是纯合二倍体,相对性状差异明显。(2)基因完全显性,每种基因的表达不受其他基因的影响。(3)减数分裂过程中,同源染色体分离机会均等,形成两类配子的数目相等或接近相等。配子都能良好地发育,并以均等的机会相互结合。(4)不同基因型合子及个体具有同等的存活率。
Crosses of two homozygous relative trait homozygous parents were inherited independently, and the hybrid offspring generally exhibited a trait separation ratio of 9:3:3:1, ie, the Mendelian ratio. However, there are many genetic instances that deviate from this ratio. This article discusses this. 1 The conditions for the emergence of the Mendelian ratio (1) The parents must be homozygous for diploids with significant differences in relative traits. (2) The gene is completely dominant, and the expression of each gene is not affected by other genes. (3) In the process of meiosis, homologous chromosomes have equal chances of segregation, and the number of two types of gametes formed is equal or nearly equal. Gametes develop well and are combined with equal opportunities. (4) Different genotype zygotes and individuals have the same survival rate.