Final answer:
The method in the question is a 'test cross,' used in genetics to determine if an individual with a dominant trait is homozygous or heterozygous by crossing it with a homozygous recessive individual.
Step-by-step explanation:
The method described is known as a test cross, which is a fundamental genetic tool used to determine an individual's genotype regarding a trait exhibiting dominant phenotype. In this method, a dominant phenotype individual whose genotype is unknown (could be homozygous dominant or heterozygous) is crossed with a homozygous recessive individual (tt). By observing the phenotypes of the offspring produced from this cross, we can deduce the genotype of the dominant phenotype parent.
If all offspring display the dominant trait, it indicates the unknown parent is homozygous dominant (TT). Conversely, if approximately half of the offspring display the dominant trait and half display the recessive trait, it implies the unknown parent is heterozygous (Tt). This classic genetic technique validates Mendel's postulate that genes come in pairs and segregate equally during gamete formation. Plant and animal breeders continue to use the test cross to ascertain the genetic composition of their breeding stock.