Practice question

Gene interaction merges phenotypic classes rather than creating novel ones because underlying genotypic segregation from independent assortment remains 9:3:3:1 while phenotypic translation changes due to pathway convergence. When two loci affect same developmental process, some genotypic combinations become phenotypically indistinguishable through masking or requirement for both dominant alleles. Complementary interaction collapses three genotypic groups containing recessive homozygotes into single white class yielding two phenotypes 9:7, duplicate dominant collapses all but double recessive yielding 15:1. Thus total distinct phenotypes never exceeds four Mendelian classes and usually appears same or fewer.