In a cross between plants with purple flowers and plants with white flowers, the offspring of `F_1` generation all had white flowers. When the `F_1` generation was self-crossed, it was observed in the `F_2` generation that out of 100, 75 flowers were white. Make a cross and answer the following questions:
The above cross is known as:

Options

A. Monohybrid cross
B. Dihybrid cross
C. Test cross
D. Back cross

Explanation

To solve the question regarding the cross between plants with purple flowers and plants with white flowers, we will follow these steps:

### Step 1: Identify the Traits
We have two traits:
- Purple flowers (dominant trait)
- White flowers (recessive trait)

### Step 2: Assign Alleles
We will assign alleles to these traits:
- Let the allele for purple flowers be represented as **W** (dominant).
- Let the allele for white flowers be represented as **w** (recessive).

### Step 3: Parental Generation (P Generation)
In the parental generation, we have:
- One plant with purple flowers (homozygous dominant): **WW**
- One plant with white flowers (homozygous recessive): **ww**

### Step 4: F1 Generation
When we cross these two plants, the offspring (F1 generation) will all have the genotype:
- **Ww** (heterozygous), which expresses the dominant trait, resulting in purple flowers.

### Step 5: Self-Crossing F1 Generation
Now, we self-cross the F1 generation (Ww x Ww):
- The gametes from each plant can be either **W** or **w**.

### Step 6: Punnett Square for F2 Generation
We can set up a Punnett square to determine the genotypes of the F2 generation:

| | W | w |
|-------|-------|-------|
| **W** | WW | Ww |
| **w** | Ww | ww |

### Step 7: Genotype and Phenotype Ratios
From the Punnett square, we can see the genotypes:
- 1 WW (homozygous dominant)
- 2 Ww (heterozygous)
- 1 ww (homozygous recessive)

This gives us a total of:
- 3 plants with purple flowers (WW and Ww)
- 1 plant with white flowers (ww)

### Step 8: Calculate the Ratios
Thus, the phenotypic ratio in the F2 generation is:
- 3 purple flowers : 1 white flower
- In percentage terms, this is 75% purple flowers and 25% white flowers.

### Conclusion: Identify the Type of Cross
Since we are only considering one trait (flower color), the cross is known as a **monohybrid cross**.

### Final Answer
The above cross is known as a **monohybrid cross**.

---