Down 's syndrome is due to

Options

A. Autosome
B. Sex chromosome
C. Sex linked disease
D. Duplication

Answer

**Step-by-Step Solution:**

1. **Understanding Down's Syndrome**: Down's syndrome is a genetic disorder characterized by a range of developmental and physical features. It is essential to recognize that it is a chromosomal disorder.

2. **Identifying the Cause**: The primary cause of Down's syndrome is an abnormal cell division that results in an extra full or partial copy of chromosome 21. This condition is known as trisomy 21.

3. **Chromosomal Basis**: Since Down's syndrome is linked to an extra chromosome, it is classified as a chromosomal disorder. Specifically, the extra chromosome is an autosome (chromosome 21 is not a sex chromosome).

4. **Evaluating the Options**:
- **Option A (Autosome)**: This is correct because Down's syndrome is caused by an extra copy of an autosome (chromosome 21).
- **Option B (Sex Chromosome)**: Incorrect, as Down's syndrome does not involve sex chromosomes.
- **Option C (Sex-linked disease)**: Incorrect, as Down's syndrome is not linked to sex chromosomes.
- **Option D (Duplication)**: Incorrect, as the disorder is due to an extra chromosome rather than a duplication of genetic material.

5. **Conclusion**: The correct answer is Option A (Autosome), as Down's syndrome is due to the presence of an extra copy of chromosome 21, which is an autosome.

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