To determine the heterozygous condition of an individual , it is crossed with the homozygous recessive counterpart .Such a cross is known as

Options

A. Reciprocal cross
B. Dihyrid cross
C. Test cross
D. Back cross

Answer

To determine the heterozygous condition of an individual, it is crossed with a homozygous recessive counterpart. This type of cross is known as a **test cross**. Here’s a step-by-step explanation of the reasoning behind this conclusion:

### Step-by-Step Solution:

1. **Understanding Genetic Terms**:
- **Homozygous**: An individual with two identical alleles for a trait (e.g., AA or aa).
- **Heterozygous**: An individual with two different alleles for a trait (e.g., Aa).
- **Recessive**: An allele that is masked by the presence of a dominant allele.

2. **Purpose of the Cross**:
- The purpose of crossing an individual with an unknown genotype (which may be heterozygous) with a homozygous recessive individual is to determine the genotype of the unknown individual.

3. **Setting Up the Cross**:
- If we denote the dominant allele as "A" and the recessive allele as "a", we can represent the unknown individual as "A_" (where "_" indicates it could be either "A" or "a").
- The homozygous recessive individual is represented as "aa".

4. **Possible Outcomes**:
- If the unknown individual is homozygous dominant (AA), all offspring will be heterozygous (Aa).
- If the unknown individual is heterozygous (Aa), the offspring will be a mix of heterozygous (Aa) and homozygous recessive (aa).

5. **Conclusion**:
- By analyzing the offspring, if all are Aa, the unknown is AA. If there are both Aa and aa offspring, the unknown is Aa.
- This method of determining the genotype of an individual by crossing it with a homozygous recessive individual is called a **test cross**.

### Final Answer:
The cross used to determine the heterozygous condition of an individual by crossing it with a homozygous recessive counterpart is known as a **test cross**.