Total 1120 seeds were obtained from a cross AaBb `xx` AaBb. Find the number of plants produced in F2 having both the resseive traits

Options

A. 210
B. 420
C. 70
D. 480

Answer

To solve the problem of finding the number of plants produced in F2 generation that exhibit both recessive traits from the cross AaBb x AaBb, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Dihybrid Cross**:
- The cross is between two heterozygous plants (AaBb x AaBb).
- This results in a dihybrid cross, which can be analyzed using a Punnett square.

2. **Determine the Genotypic Ratio**:
- For a dihybrid cross, the expected genotypic ratio is 1:2:1 for each trait.
- When combining both traits, the overall phenotypic ratio is 9:3:3:1.
- This means:
- 9 will show dominant traits for both A and B (A_B_)
- 3 will show dominant A and recessive b (A_bb)
- 3 will show recessive a and dominant B (aaB_)
- 1 will show both recessive traits (aabb)

3. **Calculate the Total Number of Offspring**:
- According to the problem, a total of 1120 seeds were obtained from the cross.

4. **Find the Proportion of Recessive Trait Plants**:
- From the phenotypic ratio, only 1 out of 16 offspring will show both recessive traits (aabb).
- Therefore, the proportion of plants with both recessive traits is 1/16.

5. **Calculate the Number of Plants with Both Recessive Traits**:
- To find the number of plants with both recessive traits, multiply the total number of seeds by the proportion:
\[ \text{Number of aabb plants} = \frac{1}{16} \times 1120 \]
- Performing the calculation:
\[ \text{Number of aabb plants} = 70 \]

### Final Answer:
The number of plants produced in F2 generation having both recessive traits (aabb) is **70**.

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