Which of the following genotype represent intersex Drosophila :-

Options

A. `2A+XXX`
B. `2A+XXY`
C. `3A+XXY`
D. `2A+XY`

Answer

To determine which genotype represents intersex Drosophila, we need to analyze the given options based on the genetic balance theory of sex determination. Here’s a step-by-step solution:

### Step 1: Understand the Genetic Balance Theory
The genetic balance theory states that the sex of Drosophila is determined by the ratio of X chromosomes to the number of sets of autosomes (A). The formula is:
\[ \text{Sex Ratio} = \frac{\text{Number of X chromosomes}}{\text{Number of sets of autosomes}} \]

### Step 2: Analyze the Options
We have the following genotypes to analyze:
1. **2A + XXX**
2. **2A + XXY**
3. **3A + YYX**
4. **2A + XY**

### Step 3: Calculate the X:A Ratios
1. **For 2A + XXX**:
- X chromosomes = 3
- Autosomes = 2
- Ratio = \( \frac{3}{2} = 1.5 \) (not intersex)

2. **For 2A + XXY**:
- X chromosomes = 2
- Autosomes = 2
- Ratio = \( \frac{2}{2} = 1 \) (intersex)

3. **For 3A + YYX**:
- X chromosomes = 1
- Autosomes = 3
- Ratio = \( \frac{1}{3} \approx 0.33 \) (not intersex)

4. **For 2A + XY**:
- X chromosomes = 1
- Autosomes = 2
- Ratio = \( \frac{1}{2} = 0.5 \) (not intersex)

### Step 4: Identify the Correct Genotype
From the calculations, the only genotype that results in a ratio indicative of intersex Drosophila is **2A + XXY**, which gives a ratio of 1.

### Final Answer
The genotype that represents intersex Drosophila is **2A + XXY**.

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