1 : 1 : 1 : 1 ratio of progenies can be obtained if the plants employed for crossing are
(A.) `"TTRR"xx"ttRR"`
(B.) `"TtRR"xx"ttrr"`
(C.) `"TtRR"xx"ttrr"`
(D.) `"TtRR" xx"ttRR"`

Options

A. A , C and D
B. A, B , C and D
C. B and D
D. A and B

Answer

To determine which of the given plant crosses will yield a 1:1:1:1 ratio of progeny, we need to analyze each option based on the principles of Mendelian genetics, particularly focusing on dihybrid crosses and the law of independent assortment.

### Step-by-Step Solution:

1. **Understanding the Genotypes**:
- We have two traits being considered: plant height (T for tall, t for dwarf) and seed shape (R for round, r for wrinkled).
- A 1:1:1:1 ratio indicates that we want to see four distinct phenotypes in equal proportions in the progeny.

2. **Analyzing Each Option**:
- **Option A: "TTRR" x "ttRR"**
- Parent 1: TTRR (homozygous tall, homozygous round)
- Parent 2: ttrr (homozygous dwarf, homozygous wrinkled)
- Progeny: All offspring will be TtRr (tall and round). No variation → Ratio: 100% TtRr.

- **Option B: "TtRR" x "ttrr"**
- Parent 1: TtRR (heterozygous tall, homozygous round)
- Parent 2: ttrr (homozygous dwarf, homozygous wrinkled)
- Progeny: TtRr (tall, round) and Ttrr (dwarf, round). No wrinkled seeds → Ratio: 50% TtRr, 50% Ttrr.

- **Option C: "TtRR" x "ttrr"**
- This option is identical to Option B. Thus, it will yield the same result → Ratio: 50% TtRr, 50% Ttrr.

- **Option D: "TtRR" x "ttRR"**
- Parent 1: TtRR (heterozygous tall, homozygous round)
- Parent 2: ttRR (homozygous dwarf, homozygous round)
- Progeny: TtRR (tall, round) and ttRR (dwarf, round). No variation → Ratio: 50% TtRR, 50% ttRR.

3. **Conclusion**:
- None of the options yield a 1:1:1:1 ratio of progeny. All options either produce only two phenotypes or do not include the recessive traits necessary for a 1:1:1:1 ratio.

### Final Answer:
None of the options (A, B, C, D) will produce a 1:1:1:1 ratio of progeny.