The 1 : 2: 1 ratio with the pink flowerin the `F_(2)` generation indicate the phenomenon of

Options

A. dominance
B. codominance
C. Incomplete dominance
D. segregation

Answer

To solve the question regarding the 1:2:1 ratio observed in the F2 generation with pink flowers, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Genetic Background**:
- In the case of flower color in Antirrhinum (snapdragon), there are two alleles involved: a dominant allele (R) for red flowers and a recessive allele (r) for white flowers.

**Hint**: Identify the alleles and their dominance relationships.

2. **Cross the Parental Generation**:
- When a pure red flower (RR) is crossed with a pure white flower (rr), all offspring in the F1 generation will be heterozygous (Rr), displaying the dominant phenotype (red flowers).

**Hint**: Determine the genotypes of the parental generation and the resulting F1 generation.

3. **Selfing the F1 Generation**:
- When the F1 generation (Rr) is self-fertilized, the genotypes of the F2 generation can be determined using a Punnett square. The possible combinations are:
- RR (homozygous dominant)
- Rr (heterozygous)
- rr (homozygous recessive)

**Hint**: Use a Punnett square to visualize the combinations of alleles in the F2 generation.

4. **Determine the Genotypic Ratio**:
- From the Punnett square, the genotypic ratio for the F2 generation is:
- 1 RR : 2 Rr : 1 rr

**Hint**: Calculate the ratio of each genotype obtained from the cross.

5. **Determine the Phenotypic Ratio**:
- The phenotypes corresponding to these genotypes are:
- RR and Rr produce red flowers.
- rr produces white flowers.
- The heterozygous Rr plants produce pink flowers due to incomplete dominance.
- Thus, the phenotypic ratio becomes:
- 1 red (RR) : 2 pink (Rr) : 1 white (rr)

**Hint**: Relate the genotypes to their respective phenotypes to find the phenotypic ratio.

6. **Identify the Phenomenon**:
- The presence of pink flowers in the F2 generation and the 1:2:1 ratio indicates the phenomenon of **incomplete dominance**. Incomplete dominance occurs when the dominant allele does not completely mask the effect of the recessive allele, resulting in a blending of traits.

**Hint**: Recall the definitions of dominance, co-dominance, and incomplete dominance to identify the correct phenomenon.

### Final Answer:
The 1:2:1 ratio with the pink flowers in the F2 generation indicates the phenomenon of **incomplete dominance**.