Practice question

Dominant epistasis occurs when dominant allele at epistatic locus masks expression of alleles at hypostatic locus regardless whether hypostatic genotype dominant or recessive. Molecularly dominant inhibitor encodes repressor or diverts metabolite. Genotypes A-B- and A-bb both show epistatic masked phenotype because presence of A sufficient, remaining 3 aaB- shows hypostatic dominant phenotype, 1 aabb double recessive. Combining 9+3 yields first class 12, resulting in 12:3:1 ratio. Summer squash white fruit W masking yellow-green color exemplifies this pattern where one dominant allele prevents pigment development despite functional color genes.