True-breeding red-eyed Drosophila flies with plain thoraxes were crossred with pink-eyed flies with striped thoraxes
`{:("Red eye",xx,"Pink eye"),("Plain thorx",,"striped throrax"):}`
The `F_(1)` flies were then test crossed against the double recessive
The following `F_(2)` generation resulted from the cross :
`{:(80,16,12,92),("Red eye","Red eye","Pink eye","Pink eye"),(underset("thorax")("Plain"),underset("thorax")("Striped"),underset("thorax")("Plain"),underset("thorax")("Striped")):}`
What percentage number of recombinats resulted from the test cross ?

Options

A. 12
B. 14
C. 16
D. 28

Answer

To solve the problem, we need to determine the percentage of recombinant offspring from the test cross of Drosophila flies. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the F2 Generation Counts
From the problem, we have the following counts of the F2 generation:
- Red-eyed plain thoraxes: 80
- Red-eyed striped thoraxes: 16
- Pink-eyed plain thoraxes: 12
- Pink-eyed striped thoraxes: 92

### Step 2: Calculate the Total Number of Offspring
To find the total number of offspring in the F2 generation, we add all the counts together:
\[ \text{Total} = 80 + 16 + 12 + 92 = 200 \]

### Step 3: Identify the Recombinant Offspring
Recombinant offspring are those that show new combinations of traits that were not present in the parental generation. In this case, the recombinant phenotypes are:
- Pink-eyed striped thoraxes (12)
- Red-eyed striped thoraxes (16)

Thus, the total number of recombinant offspring is:
\[ \text{Recombinants} = 12 + 16 = 28 \]

### Step 4: Calculate the Percentage of Recombinants
To find the percentage of recombinant offspring, we use the formula:
\[ \text{Percentage of Recombinants} = \left(\frac{\text{Number of Recombinants}}{\text{Total Offspring}}\right) \times 100 \]
Substituting the values we have:
\[ \text{Percentage of Recombinants} = \left(\frac{28}{200}\right) \times 100 = 14\% \]

### Final Answer
The percentage number of recombinants that resulted from the test cross is **14%**.

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