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

Options

A. Moderate increasesin Y complement
B. Large increase in Y complement
C. Reduction in X complement
D. increase in X complement

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about mental retardation in humans that is associated with a sex chromosomal abnormality. We need to identify the specific condition linked to this.

2. **Identifying the Chromosomal Abnormality**: The most common sex chromosomal abnormality associated with mental retardation is Klinefelter's syndrome. This condition occurs when a male has an extra X chromosome, resulting in a chromosomal pattern of XXY instead of the typical XY.

3. **Analyzing Klinefelter's Syndrome**: In Klinefelter's syndrome, the presence of an additional X chromosome can lead to various physical and developmental issues, including infertility and the development of feminine characteristics. It is also associated with cognitive impairments, which can manifest as mental retardation.

4. **Evaluating the Options**: The question likely provides multiple-choice answers. We need to assess each option:
- Moderate increase in Y complement: Incorrect, as Klinefelter's syndrome involves an increase in X, not Y.
- Large increase in Y complement: Incorrect for the same reason.
- Reduction in X complement: Incorrect, as Klinefelter's syndrome involves an increase in X.
- Increase in X complement: Correct, as Klinefelter's syndrome is characterized by the presence of an additional X chromosome (XXY).

5. **Conclusion**: Based on the analysis, the correct answer to the question is that mental retardation in men associated with sex chromosomal abnormality is usually due to an increase in X complement, specifically in the context of Klinefelter's syndrome.

**Final Answer**: Increase in X complement (Klinefelter's syndrome - XXY).

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