A white flowered mirabilis plant rr was crossed with red colour RR, If 120 plants are produced in `F_(2)` generation. The result would be :-

Options

A. 90 uniformly coloured & 30 white
B. 90 Non-uniformaly coloured & 30 white
C. 60 Non-uniformly coloured & 60 white
D. All coloured & No white

Answer

To solve the problem, we will follow these steps:

### Step 1: Understand the Genotypes
We have two parent plants:
- A white-flowered Mirabilis plant with the genotype **rr** (homozygous recessive).
- A red-flowered Mirabilis plant with the genotype **RR** (homozygous dominant).

### Step 2: Determine the F1 Generation
When we cross the two parent plants (rr x RR), all the offspring in the F1 generation will have the genotype **Rr**. Due to incomplete dominance, the phenotype of the F1 generation will be pink flowers.

### Step 3: Self-Cross the F1 Generation
Now, when we self-cross the F1 generation (Rr x Rr), we can use a Punnett square to determine the genotypic ratio:
- **R** (dominant) and **r** (recessive) can combine in the following ways:
- RR (red)
- Rr (pink)
- Rr (pink)
- rr (white)

### Step 4: Determine the Phenotypic Ratio
From the Punnett square, we can see the phenotypic ratio of the offspring:
- 1 RR (red)
- 2 Rr (pink)
- 1 rr (white)

This gives us a phenotypic ratio of **1 red : 2 pink : 1 white**.

### Step 5: Calculate the Number of Plants
Given that there are **120 plants** in the F2 generation, we can calculate the number of each phenotype:
- Total parts = 1 (red) + 2 (pink) + 1 (white) = 4 parts
- Each part = 120 plants / 4 = 30 plants

Thus:
- Red flowers (RR) = 30 plants
- Pink flowers (Rr) = 60 plants
- White flowers (rr) = 30 plants

### Step 6: Analyze the Results
From the calculations:
- There are **30 red** plants, **60 pink** plants (non-uniformly colored), and **30 white** plants.

### Conclusion
The result of the cross is:
- 30 plants are red (RR)
- 60 plants are pink (Rr)
- 30 plants are white (rr)

### Final Answer
Thus, the correct interpretation of the results is that there are **90 non-uniformly colored plants (60 pink)** and **30 white** plants.

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