An animal species has 40 chromosomes in its somatic cells. The number of chromosomes present in the somatic cells of a monosomic individual of the same species is

Options

A. 20
B. 40
C. 39
D. 19

Answer

To solve the problem, we need to determine the number of chromosomes present in the somatic cells of a monosomic individual of a species that has 40 chromosomes in its somatic cells.

### Step-by-Step Solution:

1. **Understand the Chromosome Count**:
- The question states that the animal species has 40 chromosomes in its somatic cells. In genetic terms, this means the species has a diploid number (2n) of chromosomes, where n is the number of chromosomes in a haploid cell (gametes).
- Therefore, for this species, 2n = 40.

2. **Determine the Haploid Number (n)**:
- To find the haploid number (n), we can use the relationship:
\[ n = \frac{2n}{2} = \frac{40}{2} = 20 \]

3. **Define Monosomy**:
- Monosomy refers to the condition where there is one less chromosome than the diploid number. This can be mathematically expressed as:
\[ \text{Monosomic condition} = 2n - 1 \]

4. **Calculate the Chromosome Count for a Monosomic Individual**:
- Since we know that 2n = 40, we can substitute this into the monosomy formula:
\[ 2n - 1 = 40 - 1 = 39 \]

5. **Conclusion**:
- Therefore, the number of chromosomes present in the somatic cells of a monosomic individual of the same species is **39**.

### Final Answer:
The number of chromosomes in the somatic cells of a monosomic individual is **39**.

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