(2n-1) condition of chromosomes is called :-

Options

A. tertrasomy
B. trisomy
C. monosomy
D. nullisomy

Answer

To solve the question regarding the (2n-1) condition of chromosomes, we can analyze the options provided and determine which one corresponds to this specific chromosomal condition.

### Step-by-Step Solution:

1. **Understanding Chromosomal Conditions**:
- Chromosomes are typically present in pairs, denoted as 'n' for the number of pairs. Therefore, the total number of chromosomes is represented as '2n'.
- The question asks about a condition where there is one less chromosome than the normal diploid number, which is represented as (2n-1).

2. **Analyzing the Options**:
- **Tetrasomy**: This condition involves having two extra chromosomes, leading to a total of (2n + 2). Thus, this option is incorrect.
- **Trisomy**: This condition involves having one extra chromosome, leading to a total of (2n + 1). Therefore, this option is also incorrect.
- **Monosomy**: This condition involves the loss of one chromosome from a pair, resulting in a total of (2n - 1). This matches the condition specified in the question.
- **Nullisomy**: This condition involves the loss of both chromosomes of a pair, resulting in a total of 0 chromosomes (2n - 2). Thus, this option is incorrect.

3. **Conclusion**:
- The correct answer to the question is **Monosomy**, as it corresponds to the (2n-1) condition of chromosomes.

### Final Answer:
The (2n-1) condition of chromosomes is called **Monosomy**.