In snapdragon plants, the alleles for red and ivory flower colour show incomplete dominance. When a homozygous red-flowered plant is crossed with a homozygous ivory-flowered plant, all the members of the F generation are found to bear pink flowers. Which of the following would be the outcome of crossing a red-flowered plant with a pink one?

Options

A. 1 red: 2 pink: 1 ivory
B. 3 red : 1 ivory
C. 1 red : 1 pink
D. all red

Answer

To solve the problem of crossing a red-flowered plant with a pink-flowered plant in snapdragon plants, where the alleles for red and ivory flower colors show incomplete dominance, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genotypes**:
- The homozygous red-flowered plant has the genotype **RR** (where R represents the allele for red).
- The homozygous ivory-flowered plant has the genotype **rr** (where r represents the allele for ivory).
- The pink-flowered plant, resulting from the cross of RR and rr, has the genotype **Rr** (heterozygous).

2. **Set Up the Cross**:
- We are crossing a red-flowered plant (RR) with a pink-flowered plant (Rr).
- The gametes produced by the red-flowered plant (RR) will be **R** and **R**.
- The gametes produced by the pink-flowered plant (Rr) will be **R** and **r**.

3. **Punnett Square**:
- Create a Punnett square to visualize the potential offspring from this cross.

| | R | R |
|-----|-----|-----|
| **R** | RR | RR |
| **r** | Rr | Rr |

4. **Determine the Offspring Genotypes**:
- From the Punnett square, we see the following genotypes:
- 2 offspring with genotype **RR** (red flowers)
- 2 offspring with genotype **Rr** (pink flowers)

5. **Calculate the Phenotypic Ratio**:
- The phenotypic ratio of the offspring is:
- 2 red-flowered plants (RR) : 2 pink-flowered plants (Rr), which simplifies to 1 red : 1 pink.

### Conclusion:
The outcome of crossing a red-flowered plant (RR) with a pink-flowered plant (Rr) will yield offspring in a 1:1 ratio of red to pink flowers.