In Drosophila, XXY is female. In humans it represents a male because

Options

A. Y-chromosome induces male traits in humans.
B. Y-chromsome is essential for female sex in Drosophila.
C. Y-chromosome is not essential for male sex in humans.
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Chromosomal Composition**:
- In Drosophila (fruit flies), the sex determination system is based on the ratio of X chromosomes to sets of autosomes. An XXY configuration in Drosophila is classified as female because the presence of two X chromosomes leads to female characteristics.

2. **Human Chromosomal Composition**:
- In humans, the typical male chromosomal configuration is XY, where the Y chromosome carries genes that promote male characteristics. The presence of the Y chromosome is crucial for male development.

3. **Klinefelter Syndrome**:
- The XXY configuration in humans is associated with Klinefelter syndrome. Individuals with this syndrome are genetically male (due to the presence of the Y chromosome) but may exhibit some female characteristics due to the extra X chromosome.

4. **Role of the Y Chromosome**:
- The Y chromosome contains the SRY gene (Sex-determining Region Y), which is responsible for initiating male sex determination. Therefore, despite the presence of an additional X chromosome, the Y chromosome ensures that the individual is classified as male.

5. **Conclusion**:
- In summary, the presence of the Y chromosome in the XXY configuration in humans leads to the classification as male, despite the additional X chromosome. This is why XXY represents a male in humans, while in Drosophila, it represents a female.