Test-cross | A cross between a heterozygote and the corresponding homozygous recessive. When a single trait is being studied, a test cross is a cross between an individual with the dominant phenotype but of unknown genotype (homozygous or heterozygous) with a homozygous recessive individual. If the unknown is heterozygous, then approximately 50% of the offspring should display the recessive phenotype. For example, AbC/aBc x abc/abc, where A/a, B/b and C/c represent three pairs of alleles, and the slashes separate the contributions from the two parents of each individual. |