In a plant flower colour is the example of quantitative trait and controlled by one gene pair. How many plants show parental phenotype in `F_(2)` generation:-

Options

A. `2/16`
B. `2/4`
C. `2/64`
D. `2/256`

Answer

To solve the question of how many plants show parental phenotype in the F2 generation when flower color is controlled by one gene pair, we can follow these steps:

### Step 1: Understand the Parental Generation
In this scenario, we have two parental plants:
- One with red flowers (homozygous dominant, RR)
- One with white flowers (homozygous recessive, rr)

### Step 2: Determine the F1 Generation
When we cross the two parental plants (RR x rr), all offspring in the F1 generation will be heterozygous (Rr) and will exhibit the dominant phenotype (red flowers).

### Step 3: Self-Cross the F1 Generation
Next, we self-cross the F1 generation (Rr x Rr) to produce the F2 generation.

### Step 4: Create a Punnett Square
We can create a Punnett square to visualize the possible genotypes of the F2 generation:

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

### Step 5: Analyze the Genotypes
From the Punnett square, we can see the following genotypes:
- 1 RR (homozygous dominant)
- 2 Rr (heterozygous)
- 1 rr (homozygous recessive)

### Step 6: Determine the Phenotypes
The phenotypes corresponding to these genotypes are:
- RR and Rr will show red flowers (dominant phenotype)
- rr will show white flowers (recessive phenotype)

### Step 7: Count the Parental Phenotypes
In the F2 generation, the parental phenotypes are:
- Red flowers (RR and Rr) = 3 plants
- White flowers (rr) = 1 plant

### Step 8: Calculate the Ratio
Out of the total 4 plants in the F2 generation, 3 show the red flower phenotype (parental phenotype), and 1 shows the white flower phenotype.

Thus, the ratio of plants showing parental phenotype (red flowers) to total plants is:
- 3 (red) : 1 (white)

### Final Answer
The answer to the question is that 3 out of 4 plants show the parental phenotype in the F2 generation.

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