Incomplete dominance ratio of red, pink and white in Four 'O clock is

Options

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

Answer

To solve the question regarding the incomplete dominance ratio of red, pink, and white flowers in Four O'Clock plants (Mirabilis jalapa), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Incomplete Dominance**:
- Incomplete dominance occurs when the dominant allele does not completely mask the effects of the recessive allele. Instead, the heterozygous phenotype is a blend of the two homozygous phenotypes.

2. **Identifying the Alleles**:
- In Four O'Clock plants, the alleles are represented as follows:
- **RR**: Homozygous dominant (Red flowers)
- **rr**: Homozygous recessive (White flowers)
- **Rr**: Heterozygous (Pink flowers)

3. **F1 Generation**:
- When we cross a red flower (RR) with a white flower (rr), all offspring in the F1 generation will be heterozygous (Rr), resulting in pink flowers due to incomplete dominance.

4. **Selfing the F1 Generation**:
- When we self-fertilize the F1 generation (Rr x Rr), we can use a Punnett square to determine the genotypes of the offspring:
- Possible combinations:
- RR (Red)
- Rr (Pink)
- rr (White)

5. **Determining the Phenotypic Ratio**:
- The resulting genotypic ratio from the selfing (Rr x Rr) is:
- 1 RR : 2 Rr : 1 rr
- This translates to the phenotypic ratio of:
- 1 Red : 2 Pink : 1 White

6. **Final Ratio**:
- Therefore, the ratio of red to pink to white flowers in Four O'Clock plants is **1:2:1**.

### Conclusion:
The incomplete dominance ratio of red, pink, and white flowers in Four O'Clock plants is **1:2:1**.

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