Nullisomy is represented by.....

Options

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

Answer

To determine how Nullisomy is represented, we need to understand the basic concepts of chromosome numbers in diploid organisms and how different chromosomal abnormalities are classified.

### Step-by-Step Solution:

1. **Understanding Diploid Organisms**:
- Diploid organisms have two sets of chromosomes, denoted as 2n, where "n" is the number of unique chromosomes.

2. **Identifying Chromosomal Conditions**:
- **Monosomy**: This condition is represented by 2n-1. It occurs when one chromosome from a pair is missing, resulting in only one copy of that chromosome.
- **Nullisomy**: This condition is represented by 2n-2. It occurs when both chromosomes of a homologous pair are missing, meaning there are no copies of that chromosome present.
- **Trisomy**: This condition is represented by 2n+1. It occurs when there is an extra chromosome, resulting in three copies of one chromosome.
- **Tetrasomy**: This condition is represented by 2n+2. It occurs when there are two extra chromosomes, resulting in four copies of one chromosome.

3. **Conclusion**:
- Since Nullisomy is defined as the absence of both chromosomes in a homologous pair, it is correctly represented by the formula **2n-2**.

### Final Answer:
Nullisomy is represented by **2n-2**.

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