Matting of an organism to a double recessive in order to determine whether its is homoygous or heeterozygous for a characters under consideration, is called

Options

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

Answer

To solve the question about the mating of an organism to a double recessive to determine its genotype, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- First, we need to understand the terms used in the question. The terms "homozygous" and "heterozygous" refer to the genetic makeup of an organism. Homozygous means having two identical alleles for a particular gene, while heterozygous means having two different alleles.

2. **Identifying the Cross**:
- The question describes a mating (cross) with a double recessive organism. A double recessive organism has two recessive alleles for a trait (e.g., aa for a trait where 'a' is recessive).

3. **Purpose of the Cross**:
- The purpose of this mating is to determine whether the organism in question is homozygous (AA or aa) or heterozygous (Aa) for the trait being studied.

4. **Defining the Test Cross**:
- The specific type of cross used for this purpose is known as a **test cross**. In a test cross, the organism of unknown genotype is crossed with a homozygous recessive organism. This allows us to observe the phenotypes of the offspring.

5. **Eliminating Other Options**:
- The other options provided (reciprocal cross, dihybrid cross, and back cross) do not fit the description:
- **Reciprocal Cross**: Involves crossing two organisms in both possible ways, not specifically for determining genotype.
- **Dihybrid Cross**: Involves two traits, not just one.
- **Back Cross**: Generally refers to crossing a hybrid with one of its parents, which may not necessarily involve a double recessive.

6. **Conclusion**:
- Therefore, the correct answer to the question is **test cross**.

### Final Answer:
The mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called a **test cross**.

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