Drosophila is metamale with chromosomal formulation

Options

A. 2A+3X
B. 3A+3X
C. 4A+3X
D. 3A+XY

Answer

To determine the chromosomal formulation of a metamale Drosophila, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Drosophila Sex Determination**:
- Drosophila uses the ratio of X chromosomes to autosomes for sex determination. The formula is expressed as:
\[ \text{Sex Ratio} = \frac{\text{Number of X chromosomes}}{\text{Number of Autosomes}} \]

2. **Identify the Conditions**:
- The sex determination conditions are as follows:
- Female: Ratio = 1 (1 X chromosome per 1 set of autosomes)
- Male: Ratio = 0.5 (1 X chromosome per 2 sets of autosomes)
- Metafemale: Ratio > 1 (more X chromosomes than autosomes)
- Metamale: Ratio < 0.5 (fewer X chromosomes than autosomes)
- Intersex: Ratio between 0.5 and 1

3. **Determine the Chromosomal Formula for Metamale**:
- A metamale Drosophila has a ratio of X chromosomes to autosomes that is less than 0.5.
- The typical chromosomal formulation for a metamale is represented as:
\[ \text{Chromosomal Formula} = 3A + XY \]
- Here, "A" represents the autosomes, and "XY" indicates the presence of one X and one Y chromosome.

4. **Conclusion**:
- Therefore, the correct chromosomal formulation for a metamale Drosophila is:
\[ 3A + XY \]