A pure tall Pea plant is crossed with pure dwarf Pea plant. The progeny is self pollinated. The ratio of true breeding tall Pea plants to true breeding dwarf Pea plants shall be

Options

A. `2 :1 `
B. `1 :1`
C. `3 :1`
D. `1 :2`

Answer

To solve the problem of determining the ratio of true breeding tall pea plants to true breeding dwarf pea plants after self-pollinating the progeny of a cross between a pure tall pea plant and a pure dwarf pea plant, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Parent Plants**:
- We have a pure tall pea plant (TT) and a pure dwarf pea plant (tt).
- Here, "T" represents the dominant allele for tallness, and "t" represents the recessive allele for dwarfness.

2. **Cross the Parent Plants**:
- When we cross the pure tall (TT) with the pure dwarf (tt), all offspring in the first generation (F1) will be heterozygous (Tt).
- Thus, the F1 generation consists entirely of tall plants, as the tall phenotype is dominant.

3. **Self-Pollinate the F1 Generation**:
- The next step is to self-pollinate the F1 generation (Tt x Tt).
- This will allow us to observe the segregation of traits in the next generation (F2).

4. **Use a Punnett Square**:
- Set up a Punnett square to determine the genotypes of the F2 generation:
```
T | t
----------------
T | TT | Tt
----------------
t | Tt | tt
```
- From the Punnett square, we can see the possible genotypes for the F2 generation:
- 1 TT (homozygous tall)
- 2 Tt (heterozygous tall)
- 1 tt (homozygous dwarf)

5. **Determine the Ratios**:
- The genotype ratio is 1 TT : 2 Tt : 1 tt.
- However, we are interested in true breeding plants only:
- True breeding tall plants (TT) = 1
- True breeding dwarf plants (tt) = 1

6. **Calculate the Final Ratio**:
- Therefore, the ratio of true breeding tall pea plants to true breeding dwarf pea plants in the F2 generation is:
- **1 TT : 1 tt** or simply **1:1**.

### Final Answer:
The ratio of true breeding tall pea plants to true breeding dwarf pea plants is **1:1**.

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