Practice question

In monohybrid inheritance with complete dominance, F2 generation from Tt selfing shows three genotypes TT, Tt and tt but collapses into two phenotypic classes dominant tall comprising TT and Tt and recessive dwarf tt. Number of phenotypic classes therefore two. Single class would indicate fixation, three classes implies incomplete dominance or codominance with distinct heterozygous phenotype, four classes correspond to dihybrid phenotypic array 9:3:3:1. Dominance interaction reduces genotypic diversity to binary phenotypic distinction central to Mendelian monohybrid analysis. Cytological correlation with prophase pairing, metaphase alignment and anaphase separation provides visual anchor for memorising genetic laws.