In case of co-dominance the monohybrid ratio of phenotypes in `F_(2)` generation is :-

Options

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

Answer

To solve the question regarding the monohybrid ratio of phenotypes in the F2 generation under co-dominance, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Co-Dominance**: In co-dominance, both alleles contribute to the phenotype of the organism. This means that when an individual has two different alleles (one from each parent), both traits are expressed simultaneously.

2. **Identify the Traits**: Let's consider the example of snapdragon flowers, where we have two alleles:
- Red (R) - dominant
- White (r) - recessive

3. **Parental Generation (P)**: When we cross a red flower (RR) with a white flower (rr), the offspring (F1 generation) will all be heterozygous (Rr) and will express the intermediate phenotype due to co-dominance, which in this case is pink.

4. **F1 Generation**: The F1 generation consists of all pink flowers (Rr).

5. **F2 Generation**: Now, we will cross two F1 individuals (Rr x Rr):
- Gametes produced by each parent: R and r.

6. **Punnett Square**: Set up a Punnett square to determine the genotypes of the F2 generation:
```
R r
------------
R | RR | Rr |
------------
r | Rr | rr |
------------
```

7. **Genotypes in F2**: From the Punnett square, we can see the following genotypes:
- 1 RR (Red)
- 2 Rr (Pink)
- 1 rr (White)

8. **Phenotypic Ratio**: The phenotypes corresponding to these genotypes are:
- 1 Red (RR)
- 2 Pink (Rr)
- 1 White (rr)

9. **Final Ratio**: Therefore, the phenotypic ratio in the F2 generation is 1 Red : 2 Pink : 1 White, which can be expressed as 1:2:1.

### Conclusion:
The monohybrid ratio of phenotypes in the F2 generation under co-dominance is **1:2:1**.