A test cross enables one to

Options

A. determine the viability of cross
B. distinguish between homozygous dominant and heterozygous dominant
C. determine whether two species can interbreed
D. determine the similarities in the DNA of two species

Answer

**Step-by-Step Solution:**

1. **Understanding Test Cross**: A test cross is a genetic cross performed to determine the genotype of an individual exhibiting a dominant phenotype. This is done by crossing the individual with a homozygous recessive individual.

2. **Purpose of Test Cross**: The main purpose of a test cross is to identify whether the dominant individual is homozygous dominant (AA) or heterozygous (Aa).

3. **Performing the Test Cross**:
- If the dominant individual is homozygous dominant (AA), all offspring will display the dominant phenotype (100% dominant phenotype).
- If the dominant individual is heterozygous (Aa), the offspring will display a 1:1 ratio of dominant to recessive phenotypes (50% dominant phenotype and 50% recessive phenotype).

4. **Analyzing Results**: By observing the phenotypes of the offspring from the test cross, one can determine the genotype of the dominant individual.
- If all offspring are dominant, the individual is homozygous dominant.
- If there is a mix of dominant and recessive offspring, the individual is heterozygous.

5. **Conclusion**: A test cross is a reliable method for determining the genotype of an organism that exhibits a dominant trait, thus enabling geneticists to understand inheritance patterns.

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