A test cross can be conducted to differentiate between a homozygous and a heterozygous

Options

A. dominant genotype
B. dominant phenotype
C. recessive genotype
D. recessive phenotype

Answer

### Step-by-Step Solution:

1. **Understanding Test Cross**: A test cross is a genetic cross performed to determine the genotype of an organism that exhibits a dominant phenotype. The organism in question could either be homozygous dominant (AA) or heterozygous (Aa).

2. **Mendel's Experiment**: The concept of a test cross was introduced by Gregor Mendel. He used this method to differentiate between the homozygous and heterozygous genotypes of plants that exhibited the dominant trait (for example, tall plants).

3. **Crossing with Recessive Parent**: In a test cross, the organism with the unknown genotype (dominant phenotype) is crossed with a homozygous recessive organism (aa). This allows observation of the offspring's phenotypes.

4. **Analyzing Offspring**:
- If the unknown genotype is homozygous dominant (AA), all offspring will display the dominant phenotype (tall).
- If the unknown genotype is heterozygous (Aa), the offspring will display a 1:1 ratio of dominant (tall) to recessive (dwarf) phenotypes.

5. **Conclusion**: By analyzing the phenotypes of the offspring, one can determine whether the unknown genotype was homozygous (AA) or heterozygous (Aa). If all offspring are tall, the parent is homozygous dominant. If there is a mix of tall and dwarf offspring, the parent is heterozygous.

6. **Final Answer**: Therefore, a test cross can indeed be conducted to differentiate between a homozygous and a heterozygous dominant genotype.

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