Which of the following conditions is symbolised by 2n + 2?

Options

A. Tetraploidy
B. Nullisomy
C. Trisomy
D. Tetrasomy

Answer

To determine which condition is symbolized by \(2n + 2\), we need to analyze the components of this expression step by step.

### Step-by-Step Solution:

1. **Understanding the Terms**:
- The term \(n\) refers to the haploid number of chromosomes, which is the number of chromosomes in a gamete (sperm or egg).
- The term \(2n\) indicates the diploid condition, where there are two sets of chromosomes, one from each parent. This is typical for somatic (body) cells in higher organisms.

2. **Analyzing \(2n + 2\)**:
- The expression \(2n + 2\) suggests that in addition to the normal diploid number of chromosomes (which is \(2n\)), there are 2 extra chromosomes.
- This means that there are 2 normal copies of each chromosome, plus 2 additional copies of a specific chromosome.

3. **Identifying the Condition**:
- The presence of 2 extra chromosomes indicates that there is a duplication of a specific chromosome. This condition is known as **tetrasomy**.
- In tetrasomy, there are four copies of one particular chromosome instead of the usual two.

4. **Differentiating from Other Conditions**:
- **Trisomy** refers to having an extra chromosome (i.e., \(2n + 1\)).
- **Monosomy** refers to the loss of one chromosome (i.e., \(2n - 1\)).
- **Nullisomy** refers to the complete absence of a chromosome (i.e., \(2n - 2\)).
- **Tetraploidy** refers to having four complete sets of chromosomes (i.e., \(4n\)), which is different from having extra copies of a single chromosome.

### Conclusion:
Thus, the condition symbolized by \(2n + 2\) is **tetrasomy**.

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