Mental retardation in man, associated with sex chromosomal abnormality is usually due to

Options

A. reduction in X-complement
B. increase in X-complement
C. moderate increase in Y-complement
D. large increase in Y-complement

Explanation

### Step-by-Step Solution:

1. **Identify the Condition**: The question refers to mental retardation associated with sex chromosomal abnormalities in males. The specific condition that is commonly associated with this is Klinefelter's syndrome.

2. **Understand Klinefelter's Syndrome**: Klinefelter's syndrome occurs when a male has an extra X chromosome, resulting in a chromosomal pattern of XXY instead of the typical XY.

3. **Effects of Klinefelter's Syndrome**: The presence of the extra X chromosome can lead to various physical and cognitive effects, including mental retardation. Males with this syndrome may also exhibit some female secondary sexual characteristics due to the hormonal imbalances caused by the additional X chromosome.

4. **Conclusion**: Therefore, the mental retardation in males associated with sex chromosomal abnormalities is usually due to the presence of an extra X chromosome, as seen in Klinefelter's syndrome (XXY).

### Final Answer:
Mental retardation in man, associated with sex chromosomal abnormality, is usually due to Klinefelter's syndrome (XXY).

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