The ratio of F2 generation of a dihybrid cross having pure , monohybrids , dihybrids plants is

Options

A. `1:2:1`
B. `1:2:4`
C. `1:4:8`
D. `1:1:2`

Answer

To solve the question regarding the ratio of the F2 generation of a dihybrid cross involving pure, monohybrid, and dihybrid plants, we can follow these steps:

### Step 1: Understand the Dihybrid Cross
A dihybrid cross involves two traits, each represented by two alleles. For example, let's consider two traits: A (dominant) and a (recessive) for the first trait, and B (dominant) and b (recessive) for the second trait.

### Step 2: Set Up the Parental Generation
Assume we have two pure parental lines:
- Parent 1: AABB (homozygous dominant for both traits)
- Parent 2: aabb (homozygous recessive for both traits)

### Step 3: Determine the F1 Generation
When these two parents are crossed (AABB x aabb), all offspring in the F1 generation will be heterozygous for both traits:
- F1 Generation: AaBb

### Step 4: Perform the Dihybrid Cross for F2 Generation
Now, we will cross the F1 generation with itself (AaBb x AaBb). We can use a Punnett square to determine the offspring ratios.

### Step 5: Create a Punnett Square
The gametes from each parent (AaBb) will be:
- AB, Ab, aB, ab

Setting up the Punnett square, we get:

| | AB | Ab | aB | ab |
|------|-----|-----|-----|-----|
| **AB** | AABB | AABb | AaBB | AaBb |
| **Ab** | AABb | AAbb | AaBb | Aabb |
| **aB** | AaBB | AaBb | aaBB | aaBb |
| **ab** | AaBb | Aabb | aaBb | aabb |

### Step 6: Count the Ratios
From the Punnett square, we can count the phenotypes:
- 1 AABB (homozygous dominant for both traits)
- 2 AABb (homozygous dominant for the first trait, heterozygous for the second)
- 2 AaBB (heterozygous for the first trait, homozygous dominant for the second)
- 4 AaBb (heterozygous for both traits)
- 1 AAbb (homozygous recessive for the first trait, heterozygous for the second)
- 2 Aabb (heterozygous for the first trait, homozygous recessive for the second)
- 1 aabb (homozygous recessive for both traits)

Thus, the ratio of the F2 generation is:
- 1 : 2 : 2 : 4 : 1 : 2 : 1

### Step 7: Simplify the Ratio
The simplified ratio of phenotypes for a dihybrid cross is:
- 9:3:3:1 for the dominant and recessive traits.

### Conclusion
The correct answer for the ratio of the F2 generation of a dihybrid cross is **9:3:3:1**.