Which of the following is not an aneuploid?

Options

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

Answer

To determine which of the following is not an aneuploid, we need to understand the definitions and characteristics of the terms related to chromosome number:

### Step-by-Step Solution:

1. **Understand Aneuploidy**:
- Aneuploidy refers to a condition where there is an abnormal number of chromosomes in a cell. This can occur due to the loss or gain of chromosomes during cell division.

2. **Identify Types of Aneuploidy**:
- **Monosomy**: This is a type of aneuploidy where there is a loss of one chromosome from a pair (2n-1). An example is Turner’s syndrome.
- **Trisomy**: This is another type of aneuploidy where there is an extra chromosome (2n+1). An example is Down syndrome, which involves an extra copy of chromosome 21.
- **Tetrasomy**: This involves the presence of an extra pair of chromosomes (2n+2).

3. **Evaluate the Options**:
- **Monoploid**: This term refers to having a single set of chromosomes (n), which is not an aneuploid condition. It represents a normal state without any gain or loss of chromosomes.
- The other options (monosomy, trisomy, and tetrasomy) are all forms of aneuploidy.

4. **Conclusion**:
- Since monoploid represents a normal chromosome condition without any abnormalities, it is the correct answer to the question of which option is not an aneuploid.

### Final Answer:
The option that is not an aneuploid is **Monoploid**.

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