What is a test cross used for?

A test cross is a genetic technique used primarily to determine whether an individual exhibiting a dominant phenotype is homozygous (having two identical alleles for a trait) or heterozygous (having two different alleles for a trait). By crossing the individual in question with a homozygous recessive individual, the offspring's phenotypes can provide clear insight into the genetic makeup of the parent organism.

If the dominant phenotype individual is homozygous, all offspring will display the dominant trait. Conversely, if the individual is heterozygous, approximately half of the offspring will show the recessive phenotype. This clear distinction allows researchers and breeders to understand the genetic composition of the dominant phenotype parent and is crucial for various applications in genetics, such as breeding programs and population studies.

The other options, while related to genetics, do not directly describe the purpose of a test cross. For instance, assessing genetic variability in populations or determining the age of an organism are distinct areas of genetic research that utilize different methodologies. Enhancing the breeding process could involve multiple techniques, but a test cross specifically addresses the relationship between dominant and recessive alleles.