How many genotype are produced in `F_(2)` generation in a dihybrid cross if both genes are pleiotropic -

Options

A. 3
B. 4
C. 9
D. Cannot be calculated

Answer

To determine how many genotypes are produced in the F2 generation of a dihybrid cross when both genes are pleiotropic, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Dihybrid Cross**: A dihybrid cross involves two traits, each controlled by two alleles. For example, if we denote the two traits as A/a and B/b, we are looking at the inheritance of these two traits simultaneously.

2. **Identify the Parental Generation**: In a typical dihybrid cross, we start with two heterozygous parents (AaBb x AaBb). This means each parent can produce gametes with combinations of these alleles.

3. **Gamete Formation**: Each parent can produce four types of gametes: AB, Ab, aB, and ab. Thus, when we cross two AaBb parents, we can set up a Punnett square with 16 squares (4 gametes from one parent crossing with 4 from the other).

4. **F2 Generation Genotype Ratio**: The genotypic ratio for a dihybrid cross is typically 1:2:1:2:4:2:1:2:1. This results in a total of 9 different genotypes. These genotypes can be represented as:
- AABB
- AABb
- AAbb
- AaBB
- AaBb
- Aabb
- aaBB
- aaBb
- aabb

5. **Pleiotropic Genes**: The question specifies that both genes are pleiotropic. However, it is important to note that pleiotropy affects the phenotypes produced by the alleles but does not change the number of genotypes produced. The alleles of pleiotropic genes are still inherited in the same way as alleles of single trait genes.

6. **Conclusion**: Therefore, the number of genotypes produced in the F2 generation of a dihybrid cross, regardless of whether the genes are pleiotropic, remains the same as in a regular dihybrid cross. Thus, the total number of distinct genotypes is **9**.

### Final Answer:
The total number of genotypes produced in the F2 generation of a dihybrid cross, even if both genes are pleiotropic, is **9**.

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