In an experiment of linkage, you are asked to use two pairs of characters in coupling phase in the parent. Which of the following condition will you select -

Options

A. AaBb `×x` aabb
B. AABB `×x` aabb
C. Aabb `×x` aaBb
D. Aabb `×x` aabb

Answer

To solve the question regarding the selection of conditions for an experiment of linkage using two pairs of characters in the coupling phase in the parent, we will follow these steps:

### Step-by-Step Solution:

1. **Understand Linkage**: Linkage refers to the tendency of genes that are located close to each other on a chromosome to be inherited together. In linkage, the parental combinations of traits are more frequent than new combinations (recombinants).

**Hint**: Remember that linkage results in fewer recombinants compared to parental combinations.

2. **Define Coupling Phase**: In the coupling phase, both dominant alleles (e.g., A and B) are on one chromosome, and both recessive alleles (e.g., a and b) are on the homologous chromosome.

**Hint**: Coupling phase means that the alleles are inherited together.

3. **Analyze the Options**: We need to analyze the provided options to see which one gives us a higher proportion of parental combinations compared to recombinant combinations.

4. **Evaluate Each Option**:
- **Option A**: Capital A small a, Capital B small b vs. small a small a, small b small b
- Gametes produced: AB, Ab, aB, ab
- Parental combinations are not more than 50%.

- **Option B**: Capital A small a, small b small b vs. small a small a, Capital B small b
- Gametes produced: AB, Ab, aB, ab
- This option shows higher recombination as well.

- **Option C**: Capital A small a, Capital B small b vs. small a small a, small b small b
- Gametes produced: AB, Ab, aB, ab
- Again, the parental combinations are not more than 50%.

- **Option D**: Capital A small a, small b small b vs. small a small a, Capital B small b
- Gametes produced: AB, Ab, aB, ab
- This option shows a balance of parental and recombinant combinations.

5. **Select the Best Option**: After evaluating all options, we find that the option that provides the highest parental combination with minimal recombination is the one where both dominant alleles are coupled together.

**Final Answer**: The best condition to select for the experiment is **Option D**, where the parental combinations are maximized.

### Summary of the Solution:
To select the appropriate condition for linkage experiments, we analyze the parental and recombinant combinations from the given options. The option that maintains a higher ratio of parental combinations indicates successful linkage.