Which of the following represent monosomy .

Options

A. 2n-1
B. 2n+1
C. 2n-2
D. 2n+2

Answer

To solve the question "Which of the following represent monosomy?", we need to understand what monosomy means in the context of genetics.

### Step-by-Step Solution:

1. **Understand Monosomy**: Monosomy is a type of aneuploidy where one chromosome from a pair is missing. In a normal diploid organism, the chromosome number is represented as 2n, where n is the number of pairs of chromosomes.

2. **Identify the Chromosome Number in Monosomy**: If an organism has a normal diploid number of chromosomes (2n), and one chromosome is missing, the chromosome number would be represented as 2n - 1. For example, in humans, the normal diploid number is 46 (2n = 46). If one chromosome is missing, it would be 46 - 1 = 45.

3. **Evaluate the Options**:
- **Option A: 2n - 1**: This represents monosomy as it indicates one chromosome is missing.
- **Option B: 2n + 1**: This indicates an extra chromosome, which is not monosomy.
- **Option C: 2n - 2**: This indicates two chromosomes are missing, which is not monosomy.
- **Option D: 2n + 2**: This indicates two extra chromosomes, which is also not monosomy.

4. **Conclusion**: The only option that correctly represents monosomy is **Option A: 2n - 1**.

### Final Answer:
**A: 2n - 1**