Trisomy is represented by

Options

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

Answer

To solve the question regarding the representation of trisomy, we need to understand the concept of chromosomal abnormalities, particularly aneuploidy. Here’s a step-by-step breakdown:

### Step-by-Step Solution:

1. **Understanding Chromosomal Disorders**:
- Chromosomal disorders arise due to the absence, excess, or abnormal arrangement of chromosomes.
- These disorders can be classified into different types based on the number of chromosomes present.

2. **Defining Terms**:
- **Diploid Number (2n)**: This represents the normal number of chromosomes in a somatic cell. For humans, n = 23, so 2n = 46.
- **Aneuploidy**: This is a condition where the number of chromosomes is not an exact multiple of the haploid number. It includes conditions like monosomy, trisomy, and tetrasomy.

3. **Identifying Monosomy**:
- Monosomy is represented by **2n - 1**, indicating that one chromosome from a pair is missing.
- Example: Turner syndrome (45 chromosomes, missing one X chromosome).

4. **Identifying Tetrasomy**:
- Tetrasomy is represented by **2n + 2**, indicating that there are two extra chromosomes.
- This means there are four chromosomes of a particular type instead of the normal two.

5. **Identifying Trisomy**:
- Trisomy is represented by **2n + 1**, which means there is one extra chromosome in addition to the normal diploid set.
- An example of trisomy is Down syndrome, which is caused by an extra copy of chromosome 21 (47 chromosomes total).

6. **Conclusion**:
- Based on the definitions and examples, the representation for trisomy is **2n + 1**.

### Final Answer:
Trisomy is represented by **2n + 1**.

---