Which of the following crosses will give tall and dwarf pea plants in same proportions ?

Options

A.
B.
C.
D.

Explanation

To determine which of the given crosses will yield tall and dwarf pea plants in the same proportions, we need to analyze each option based on Mendelian genetics. The desired ratio of tall to dwarf plants is 1:1.

### Step-by-Step Solution:

1. **Understanding the Genotypes**:
- Tall pea plants are represented by the dominant allele (T), while dwarf plants are represented by the recessive allele (t).
- A plant can be either homozygous dominant (TT), heterozygous (Tt), or homozygous recessive (tt).

2. **Analyzing Option A (TT x tt)**:
- Cross: TT (tall) x tt (dwarf)
- Progeny: All offspring will be Tt (tall).
- Ratio: 100% tall, 0% dwarf.
- Conclusion: This option does not yield a 1:1 ratio.

3. **Analyzing Option B (Tt x tt)**:
- Cross: Tt (tall) x tt (dwarf)
- Progeny: Possible combinations are Tt (tall) and tt (dwarf).
- Ratio: 1 tall (Tt) : 1 dwarf (tt).
- Conclusion: This option yields a 1:1 ratio, making it a test cross.

4. **Analyzing Option C (TT x Tt)**:
- Cross: TT (tall) x Tt (tall)
- Progeny: Possible combinations are TT (tall) and Tt (tall).
- Ratio: 75% tall, 25% dwarf.
- Conclusion: This option does not yield a 1:1 ratio.

5. **Analyzing Option D (tt x tt)**:
- Cross: tt (dwarf) x tt (dwarf)
- Progeny: All offspring will be tt (dwarf).
- Ratio: 100% dwarf, 0% tall.
- Conclusion: This option does not yield a 1:1 ratio.

### Final Conclusion:
The correct answer is **Option B (Tt x tt)**, as it produces tall and dwarf pea plants in a 1:1 ratio.

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