Find out the % of plants, which are dominant for both the character by the cross of `(,,)/(ab)` ab with it's recessive form, if 20% recombination is present:-

Options

A. 0.1
B. 0.2
C. 0.45
D. 0.4

Answer

To solve the problem of finding the percentage of plants that are dominant for both characters from the cross of `(AB)/(ab)` with its recessive form, given that there is a 20% recombination frequency, we can follow these steps:

### Step 1: Understand the Cross
We are crossing two parental genotypes: one homozygous dominant `(AB)` and one homozygous recessive `(ab)`. The gametes produced by these parents will be `AB` from the first parent and `ab` from the second parent.

### Step 2: Determine the Recombinant Frequency
The problem states that there is a 20% recombination frequency. This means that 20% of the offspring will be recombinant types, while the remaining 80% will be parental types.

### Step 3: Calculate the Percentage of Parental Types
Since 20% of the offspring are recombinants, the percentage of parental types is:
\[ 100\% - 20\% = 80\% \]

### Step 4: Distribute the Parental Types
The parental types consist of the original combinations of alleles:
- `AB` (dominant for both traits)
- `ab` (recessive for both traits)

Since there are two parental types and they contribute equally to the total parental percentage, we divide the parental percentage by 2:
\[ \text{Percentage of } AB = \frac{80\%}{2} = 40\% \]

### Step 5: Conclusion
Thus, the percentage of plants that are dominant for both characters (i.e., those with the genotype `AB`) is 40%.

### Final Answer
The percentage of plants that are dominant for both characters is **40%**.

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