The symptoms of a genetic disorder are short- statured with a small round head , furrowed tongue and partially open mouth. Such a genetic disorder is characterized by the presence of an extra chromosome number ………..

Options

A. 20
B. 21
C. 17
D. 23

Answer

To solve the question regarding the genetic disorder characterized by specific symptoms, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Symptoms**: The symptoms described in the question include:
- Short stature
- Small round head
- Furrowed tongue
- Partially open mouth

2. **Recognize the Genetic Disorder**: The symptoms listed are characteristic of Down syndrome, which is a well-known genetic disorder.

3. **Understand the Genetic Basis**: Down syndrome is caused by the presence of an extra chromosome. This condition is specifically known as trisomy 21, meaning there are three copies of chromosome 21 instead of the usual two.

4. **Determine the Extra Chromosome Number**: Since Down syndrome is associated with an extra copy of chromosome 21, the answer to the question regarding the extra chromosome number is 21.

5. **Select the Correct Option**: Among the options provided (20, 21, 17, 23), the correct answer is 21.

### Final Answer:
The genetic disorder is characterized by the presence of an extra chromosome number **21**.

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