Question

Sol.(c) [Key Concept: Test Cross — F1 with Double Recessive] Test cross involves crossing the F1 HYBRID (dominant phenotype, unknown genotype) with a DOUBLE RECESSIVE genotype (aabb or aa). The double recessive parent produces only recessive gametes, making the offspring phenotypes a direct readout of the gametes (and hence genotype) of the F1 hybrid. This is the standard procedure for determining whether F1 is homozygous dominant (AA) or heterozygous (Aa).