Mark the odd one (w.r.t. `F_(2)` generation of Mendelian dihybrid cross)

Options

A. Frequency of TtRR genotype `= 12.5%`
B. Frequency of ttrr genotype `= 6.25%`
C. Frequency of TTRR genotype `= 6.25%`
D. Frequency of TTRR genotype `= 25%`

Answer

To solve the question of marking the odd one out with respect to the F2 generation of a Mendelian dihybrid cross, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Dihybrid Cross**:
- In a dihybrid cross, we are examining two traits simultaneously. In this case, we have two traits: height (Tall - T, Dwarf - t) and seed shape (Round - R, Wrinkled - r).

2. **Identify the Parental Genotypes**:
- The parental plants are pure homozygous for both traits: one parent is TTRR (tall and round), and the other is ttrr (dwarf and wrinkled).

3. **Determine the F1 Generation**:
- The F1 generation from crossing TTRR and ttrr will be all heterozygous: TtRr (tall and round).

4. **Self-Cross the F1 Generation**:
- The F1 plants (TtRr) are self-crossed to produce the F2 generation. The gametes produced will be TR, Tr, tR, and tr.

5. **Construct the Punnett Square**:
- A Punnett square for the F1 cross (TtRr x TtRr) will yield 16 possible combinations in the F2 generation.

6. **Count the Genotypes**:
- From the Punnett square, we can count the occurrences of each genotype:
- TTRR (tall and round) = 1
- TtRR (tall and round) = 2
- TTRr (tall and round) = 2
- TtRr (tall and round) = 4
- ttRR (dwarf and round) = 1
- ttRr (dwarf and round) = 2
- TTRr (tall and round) = 2
- ttrr (dwarf and wrinkled) = 1

7. **Calculate Frequencies**:
- Total genotypes = 16
- Frequency of TTRR = 1/16 = 6.25%
- Frequency of tt (dwarf wrinkled) = 1/16 = 6.25%
- Frequency of TTRR (homozygous tall and round) = 1/16 = 6.25%
- Frequency of TTRR (homozygous tall and round) = 1/16 = 6.25%

8. **Identify the Odd One Out**:
- The last option states the frequency of TTRR as 25%, which is incorrect. All other frequencies calculated are correct (6.25% for TTRR, tt, and TTRR).

9. **Conclusion**:
- The odd one out is the option stating the frequency of TTRR as 25%.

### Final Answer:
The odd one out is the option that states the frequency of TTRR as 25%.