Heteropycnosis is exhibited by

Options

A. Autosome
B. Chromatid body
C. Nucleolus
D. Sex chromosome

Answer

**Step-by-Step Solution:**

1. **Understanding Heteropycnosis**: Heteropycnosis is a phenomenon observed in certain chromosomes where specific regions stain more intensely than others. This indicates differences in chromatin structure and density.

2. **Chromatin Types**: There are two main types of chromatin:
- **Heterochromatin**: This type of chromatin is densely packed and stains darker. It is often associated with gene repression.
- **Euchromatin**: This type is less densely packed and stains lighter, typically associated with active gene expression.

3. **Positive and Negative Heteropycnosis**:
- **Positive Heteropycnosis**: Occurs when heterochromatin stains darker than euchromatin.
- **Negative Heteropycnosis**: Occurs when heterochromatin stains lighter than euchromatin.

4. **Examples of Heteropycnosis**:
- A well-known example of heteropycnosis is observed in the X chromosome of Drosophila (fruit flies) and grasshoppers during spermatogenesis. In these organisms, the X chromosome exhibits heteropycnosis, showing distinct staining patterns.

5. **Identifying the Correct Answer**: The question asks which type of chromosome exhibits heteropycnosis. Based on the examples and definitions provided:
- The correct answer is **sex chromosomes**, as they are known to exhibit heteropycnosis, particularly in species like Drosophila and grasshoppers.

**Final Answer**: Heteropycnosis is exhibited by **sex chromosomes**.

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