What is the purpose of a test cross in genetics?

A test cross is a breeding experiment designed to reveal the genotype of an organism exhibiting a dominant phenotype. By crossing the organism with a homozygous recessive individual, the offspring's phenotypes can be analyzed. If any offspring display the recessive phenotype, it indicates that the dominant phenotype parent carries at least one recessive allele, confirming that the genotype is heterozygous. If all offspring show the dominant phenotype, it suggests that the dominant phenotype parent is likely homozygous.

The purpose of a test cross is fundamentally about identifying and clarifying unknown genotypes, particularly for individuals that display a dominant phenotype. This method is critical for genetic studies and breeding programs where understanding the genetic makeup of an organism can inform predictions about future generations. The other options do not capture this primary function of the test cross as effectively.