In genetics, what is the expected outcome when an unknown genotype is crossed with a homozygous recessive individual?

• A. Increased variation
• B. Test cross analysis
• C. Predictable results
• D. Null results

Answer: (B)

When an unknown genotype is crossed with a homozygous recessive individual, this situation is commonly referred to as a test cross. The purpose of conducting a test cross is to determine the genotype of the unknown individual. By mating the unknown genotype with a homozygous recessive individual, the outcomes of the offspring can provide clear insights into whether the unknown individual is homozygous dominant or heterozygous.

If the offspring exhibit the dominant phenotype, it indicates that the unknown parent is likely homozygous dominant or heterozygous. Conversely, if any offspring display the recessive phenotype, it confirms that the unknown parent is heterozygous, as the recessive phenotype can only appear if at least one recessive allele is inherited from the unknown parent.

This method allows for a predictable interpretation of the results based on the phenotypes of the resulting offspring, making it an essential tool in genetics for identifying unknown genotypes.