What is a test cross utilized for?

• A. To identify phenotypic expressions
• B. To determine unknown genotypes
• C. To track inheritance patterns
• D. To sequence DNA

Answer: (B)

A test cross is a breeding experiment used to determine the genotype of an organism exhibiting a dominant phenotype. This is achieved by crossing the individual in question with a homozygous recessive individual. If the organism’s genotype is homozygous dominant, all offspring will display the dominant phenotype. However, if the organism’s genotype is heterozygous, the offspring will show a mix of both dominant and recessive phenotypes.

This method effectively reveals the unknown genotype of the organism based on the ratio of phenotypes observed in the offspring. Understanding the genotype is crucial for genetic studies, breeding practices, and exploring inheritance patterns.

The other options do not align with the primary use of a test cross. Identifying phenotypic expressions, while related, does not directly pertain to determining genotypes. Tracking inheritance patterns is a broader concept that encompasses several methods beyond just test crosses. Sequencing DNA is a molecular technique that focuses on the nucleotide sequence rather than on genotype determination through breeding experiments. Therefore, using a test cross specifically addresses the need to reveal unknown genotypes within the context of genetics.