Practice question

Independent assortment principle states alleles at unlinked loci orient randomly on metaphase plate independently of other loci, producing equal parental and recombinant gamete frequencies. In cross AaBb x AaBb this random orientation yields F2 phenotypic distribution 9 A-B- :3 A-bb :3 aaB- :1 aabb, where 9 represents both dominant traits together. Product of two 3:1 monohybrid ratios mathematically. Significant excess of parental phenotypes indicates linkage with reduced recombination, while collapsing of classes into fewer phenotypes signals epistatic interaction. Therefore intact 9:3:3:1 remains diagnostic hallmark of two unlinked genes with complete dominance.