Trisomy of chromosome 21 causes:

Options

A. Klinefelter's syndrome
B. Tuner's syndrome
C. Sickle cell anaemia
D. Down's syndrome

Answer

**Step-by-Step Solution:**

1. **Understanding Trisomy**: Trisomy is a genetic condition where an individual has three copies of a particular chromosome instead of the normal two. This results in a total of 47 chromosomes instead of the usual 46.

2. **Identifying Chromosome 21**: In the case of Trisomy 21, there is an extra copy of chromosome 21. This condition is also known as Down syndrome.

3. **Reviewing the Options**:
- **Option A: Klinefelter Syndrome**: This condition is caused by the presence of an additional X chromosome in males (XXY), not related to chromosome 21.
- **Option B: Turner Syndrome**: This is a condition where one X chromosome is missing in females (45, X), which is an example of monosomy, not trisomy.
- **Option C: Sickle Cell Anemia**: This is a genetic disorder caused by a point mutation in the hemoglobin gene, unrelated to chromosome 21.
- **Option D: Down Syndrome**: This is the condition caused by Trisomy 21, where individuals have an extra chromosome 21.

4. **Conclusion**: Based on the analysis of the options, the correct answer is **Down syndrome**, which is caused by Trisomy of chromosome 21.

**Final Answer**: Trisomy of chromosome 21 causes Down syndrome.

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