In the `F_(2)` generation a Mendelian dihybrid cross the number of phenotypes and genotypes are

Options

A. phenotypes-4 genotypes-16
B. phenotypes-9, genotypes-4
C. phenotypes-4, genotypes-8
D. phenotypes-4, genotypes-9

Explanation

To solve the question regarding the number of phenotypes and genotypes in the F2 generation of a Mendelian dihybrid cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Dihybrid Cross**:
A dihybrid cross involves two traits, each represented by two alleles. For example, consider traits for seed shape (round vs. wrinkled) and seed color (yellow vs. green).

2. **Identify Parental Generation (P)**:
Let's assume we are crossing two true-breeding plants: one with round yellow seeds (RRYY) and another with wrinkled green seeds (rryy).

3. **Determine F1 Generation**:
The F1 generation will all be heterozygous for both traits (RrYy), showing the dominant phenotypes (round yellow seeds).

4. **Perform F1 Self-Cross**:
To find the F2 generation, we cross two F1 individuals (RrYy x RrYy).

5. **Use Punnett Square**:
Create a 4x4 Punnett square to determine the genotypes of the F2 generation. Each parent can produce four types of gametes: RY, Ry, rY, and ry.

6. **Count Genotypes**:
After filling in the Punnett square, we find the following genotypic ratios:
- 1 RRYY (homozygous round yellow)
- 2 RrYY (heterozygous round yellow)
- 1 rrYY (homozygous round yellow)
- 2 RRYy (homozygous round yellow)
- 4 RrYy (heterozygous round yellow)
- 2 Rryy (heterozygous wrinkled yellow)
- 1 rryy (homozygous wrinkled green)

This gives us a total of 9 different genotypes.

7. **Count Phenotypes**:
The phenotypes resulting from the F2 generation can be summarized as:
- Round Yellow (R_Y): 9
- Round Green (R_yy): 3
- Wrinkled Yellow (rrY_): 3
- Wrinkled Green (rryy): 1

This results in a total of 4 distinct phenotypes.

8. **Conclusion**:
Therefore, in the F2 generation of a Mendelian dihybrid cross, the number of phenotypes is 4, and the number of genotypes is 9.

### Final Answer:
- **Phenotypes**: 4
- **Genotypes**: 9

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