Q.The genotype of a plant showing the dominant phenotype can be determined by

A test cross is a cross between an individual of unknown genotype - typically one showing a dominant phenotype - and a homozygous recessive individual, carried out specifically to reveal the unknown individual's genotype. Because the homozygous recessive parent contributes only recessive alleles, it cannot mask anything, so the phenotype ratio among the offspring directly reflects the gamete types the unknown parent produced: if the unknown parent is homozygous dominant, every offspring shows the dominant phenotype (no segregation); if it is heterozygous, the offspring split 1:1 between the dominant and recessive phenotypes, revealing that it was carrying a hidden recessive allele all along. Mendel devised the test cross specifically because a dominant phenotype …