What genetic technique is used to determine the genotype of an organism with a dominant phenotype?

The test cross is a valuable genetic technique used to determine the genotype of an organism exhibiting a dominant phenotype. This approach involves breeding the organism in question with another organism that is homozygous recessive for the trait of interest. By observing the phenotypes of the offspring produced, one can infer the genotype of the parent with the dominant phenotype.

If the dominant phenotype parent is homozygous dominant, all offspring will display the dominant phenotype. Conversely, if the parent is heterozygous, approximately half of the offspring will exhibit the dominant phenotype, while the other half will show the recessive phenotype. This distinction allows researchers to ascertain whether the dominant phenotype individual is homozygous or heterozygous.

In contrast, cross breeding typically refers to the process of mating two organisms generally for the purpose of producing offspring and does not specifically target genotype determination. Back cross refers to mating an F1 hybrid with one of its parents, which is also not primarily focused on identifying genotype. Population sampling involves assessing alleles and genotypes in a population but does not provide the direct insight necessary for identifying the genotype of an individual organism.