XY chromosomes are

Options

A. Homomorphic
B. Heteromorphic
C. Heterologous
D. Both B and C

Answer

### Step-by-Step Solution:

1. **Understanding Chromosomes**:
- Chromosomes are structures within cells that contain DNA. They play a crucial role in inheritance and the functioning of organisms.

2. **Types of Chromosomes**:
- There are two main types of chromosomes:
- **Autosomes**: These chromosomes do not determine the sex of an organism and are involved in general traits.
- **Sex Chromosomes**: These chromosomes determine the sex of an organism. In humans, the sex chromosomes are X and Y.

3. **Identifying XY Chromosomes**:
- The XY chromosomes refer specifically to the male sex chromosomes, where the presence of one X and one Y chromosome indicates a male individual.

4. **Characteristics of XY Chromosomes**:
- The X and Y chromosomes are different in terms of shape, size, and function. This difference is why they are classified as heteromorphic chromosomes.
- **Heteromorphic**: The term 'heteromorphic' means that the chromosomes are different in physical appearance. "Hetero" means different, and "morphic" refers to form or shape.

5. **Specific Differences**:
- The X chromosome is classified as **metacentric**, meaning its centromere is located in the middle, giving it a more symmetrical appearance.
- The Y chromosome is classified as **acrocentric**, meaning its centromere is located closer to one end, resulting in an asymmetrical shape.

6. **Conclusion**:
- Therefore, the answer to the question "XY chromosomes are ___" is **heteromorphic**.