Edward's syndrome characterized by mental deficiency is caused by trisomy of chromosome
(a) 5
(b) 9
(c) 15
(d) 18

Options

A. 5
B. 9
C. 15
D. 18

Answer

**Step-by-Step Solution:**

1. **Understanding Edwards Syndrome**: Edwards syndrome is a genetic disorder that is characterized by various physical and developmental challenges, including mental deficiency.

2. **Identifying the Cause**: The syndrome is specifically caused by the presence of an extra chromosome, which is referred to as trisomy. In the case of Edwards syndrome, this involves an extra copy of a specific chromosome.

3. **Chromosome Number**: The question requires us to identify which chromosome is involved in this trisomy. The options provided are chromosomes 5, 9, 15, and 18.

4. **Recognizing Trisomy 18**: Edwards syndrome is also known as trisomy 18. This means that individuals with this syndrome have three copies of the 18th chromosome instead of the usual two.

5. **Selecting the Correct Answer**: Since we have established that Edwards syndrome is caused by trisomy of the 18th chromosome, the correct answer is (d) 18.

**Final Answer**: (d) 18

---