The number of chromossomes in Down's syndrome is

Options

A. 46
B. 47
C. 45
D. 23

Answer

**Step-by-Step Solution:**

1. **Understanding Down's Syndrome**: Down's syndrome is a genetic disorder caused by the presence of an extra chromosome.

2. **Normal Chromosome Count**: In humans, the typical number of chromosomes is 46, which consists of 23 pairs.

3. **Identifying the Extra Chromosome**: In Down's syndrome, there is an additional chromosome, specifically an extra copy of chromosome 21.

4. **Counting the Total Chromosomes**: Due to this extra chromosome, individuals with Down's syndrome have a total of 47 chromosomes instead of the normal 46.

5. **Terminology**: Down's syndrome is also referred to as "trisomy 21" because of the presence of three copies of chromosome 21.

6. **Conclusion**: Therefore, the number of chromosomes in Down's syndrome is 47.

**Final Answer**: The number of chromosomes in Down's syndrome is 47.

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