In a cross between true red flowered (RR) and true breeding white flowered (rr), snapdragon plant, the `F_(1)(Rr)` was pink. When the `F_(1)` was self pollinated the `F_(2)` resulted in the following ratio 1(RR) red, 2(Rr) pink, 1(rr) white. Above condition can be explained by-

Options

A. True dominance
B. Incomplete dominance
C. Lethal gene
D. Independent assortment

Answer

To solve the question about the inheritance pattern observed in snapdragon plants, we will follow these steps:

### Step 1: Understand the Parent Generation
In the given scenario, we have two true breeding parents:
- True red flowered snapdragon (RR)
- True breeding white flowered snapdragon (rr)

### Step 2: Determine the F1 Generation
When these two parents are crossed, the F1 generation consists of all heterozygous individuals (Rr). According to the problem, the flowers of the F1 generation are pink. This indicates that the red allele (R) does not completely dominate the white allele (r), leading to a blending of traits.

### Step 3: Self-Pollination of F1 Generation
Next, when the F1 generation (Rr) is self-pollinated, we need to determine the genotypes of the F2 generation.

### Step 4: Use a Punnett Square
To find the expected genotypic ratio in the F2 generation, we can set up a Punnett square:

```
R r
----------------
R | RR | Rr |
----------------
r | Rr | rr |
----------------
```

From the Punnett square, we can see the following combinations:
- 1 RR (homozygous red)
- 2 Rr (heterozygous pink)
- 1 rr (homozygous white)

### Step 5: Determine the Phenotypic Ratio
The phenotypic ratio from the F2 generation is:
- 1 Red (RR)
- 2 Pink (Rr)
- 1 White (rr)

This results in a ratio of 1:2:1.

### Step 6: Identify the Genetic Principle
The observed ratio and the blending of traits in the F1 generation suggest that this inheritance pattern is due to **incomplete dominance**. Incomplete dominance occurs when neither allele is completely dominant over the other, resulting in a phenotype that is a blend of both traits.

### Conclusion
The condition described in the question can be explained by the phenomenon of **incomplete dominance**.

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