Mating of an organism to double ressive for detemining homozygosity or heterozygosity is

Options

A. Reciprocal cross
B. Backcross
C. Dihybrid cross
D. Test cross

Answer

To determine whether an organism is homozygous or heterozygous, we can perform a specific type of mating known as a test cross. Here’s a step-by-step explanation of the process:

### Step-by-Step Solution:

1. **Understanding the Problem**:
- We need to determine if an organism exhibiting a dominant phenotype is homozygous dominant (AA) or heterozygous (Aa).

2. **Identifying the Test Cross**:
- A test cross involves mating the organism in question with a double recessive organism (aa). The double recessive organism will only produce recessive phenotypes.

3. **Performing the Cross**:
- If the organism is homozygous dominant (AA), all offspring from the test cross will exhibit the dominant phenotype (A).
- If the organism is heterozygous (Aa), the offspring will show a mix of dominant and recessive phenotypes (A and a).

4. **Analyzing the Results**:
- After performing the test cross, observe the phenotypes of the offspring.
- If all offspring display the dominant phenotype, the original organism is homozygous dominant (AA).
- If there is a 1:1 ratio of dominant to recessive phenotypes, the original organism is heterozygous (Aa).

5. **Conclusion**:
- The mating of an organism to a double recessive for determining homozygosity or heterozygosity is called a **test cross**.