Final answer:
A cross between an individual with a dominant phenotype and one that is homozygous recessive is known as a test cross. It helps determine if the dominant-expressing parent is heterozygous or homozygous for the dominant trait.
Step-by-step explanation:
The cross of an individual who has a dominant phenotype with an individual who is homozygous recessive for that gene is known as a test cross. This type of cross is used to determine the genotype of an organism that expresses the dominant trait but has an unknown genotype. During a test cross, the offspring's phenotypes can help indicate whether the unknown parent is heterozygous (carrying one dominant and one recessive allele) or homozygous dominant (carrying two dominant alleles).
For instance, if a plant with a dominant flower color is crossed with one that is homozygous for the recessive flower color, the resulting offspring can help determine the genotype of the dominant expressing plant. If all offspring exhibit the dominant trait, the parent is likely homozygous dominant. If there is a 1:1 ratio of dominant to recessive phenotypes in the offspring, the parent is heterozygous. The test cross is a crucial tool for understanding Mendelian inheritance patterns and is still used in plant and animal breeding today.