A pure breeding triangular fruit bearing plant of Shepherd's Purse is crossed with ovoid fruit bearing plant. The ratio of two types of plants in `F_(2)` generation would be

Options

A. `3:1`
B. `1:2:1`
C. `13:3`
D. `15:1`

Answer

To solve the problem of determining the phenotypic ratio of triangular to ovoid fruit-bearing plants in the F2 generation of Shepherd's Purse, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Traits**:
- The triangular fruit shape is dominant (let's assign it the genotype A_B_).
- The ovoid fruit shape is recessive (genotype aa bb).

2. **Determine the Parental Cross**:
- The pure breeding triangular fruit plant (AA BB) is crossed with the pure breeding ovoid fruit plant (aa bb).

3. **F1 Generation**:
- All offspring in the F1 generation will be heterozygous (Aa Bb) since they inherit one allele from each parent. Thus, all F1 plants will exhibit the dominant triangular fruit shape.

4. **Self-Pollination of F1 Generation**:
- When the F1 plants (Aa Bb) are self-pollinated, we need to determine the gametes produced. The gametes from Aa Bb can be:
- AB
- Ab
- aB
- ab

5. **Punnett Square**:
- Set up a Punnett square to cross the gametes:
```
AB Ab aB ab
-----------------------
AB | AABB AABb AaBB AaBb
Ab | AABb AAbb AaBb Aabb
aB | AaBB AaBb aaBB aaBb
ab | AaBb Aabb aaBb aabb
```

6. **Count the Phenotypes**:
- Now, we count the phenotypes from the Punnett square:
- Triangular (A_B_): AABB, AABb, AaBB, AaBb (9 combinations)
- Ovoid (aa bb): aabb (1 combination)

7. **Calculate the Ratio**:
- The phenotypic ratio of triangular to ovoid plants in the F2 generation is:
- Triangular: 15 (A_B_ combinations)
- Ovoid: 1 (aa bb combination)
- Therefore, the ratio is 15:1.

8. **Final Answer**:
- The ratio of triangular to ovoid fruit-bearing plants in the F2 generation is **15:1**.