Test cross
![Punnett squares showing typical test crosses and the two potential outcomes. The individual in question may either be heterozygous, in which half the offspring would be heterozygous and half would be homozygous recessive, or homozygous dominant, in which all the offspring would be heterozygous.](/Images/godic/202502/15/Punnett_Square_Test_Cross5412.PNG")
In genetics, a test cross, first introduced by Gregor Mendel, involves the breeding of an individual with a phenotypically recessive individual, in order to determine the zygosity of the former by analyzing proportions of offspring phenotypes. Zygosity can either be heterozygous or homozygous. Those that are heterozygous have one dominant and one recessive allele. Individuals that are homozygous dominant have two dominant alleles, and those that are homozygous recessive have two recessive alleles.