Centromere are-

Options

A. Constricted regions of chromosomes
B. Regions where microtubules polymerise
C. Part of Cilia
D. The central part of the same cell

Answer

**Step-by-Step Text Solution:**

1. **Understanding Chromosomes**: Chromosomes are structures within cells that contain DNA. They are made up of chromatin, which is a complex of DNA and proteins.

2. **Identifying Chromatids**: During cell division, each chromosome is replicated, resulting in two identical halves known as sister chromatids. These chromatids are connected at a specific region.

3. **Defining the Centromere**: The centromere is the specific region where the two sister chromatids are joined together. It is often referred to as the primary constriction of the chromosome.

4. **Characteristics of the Centromere**: The centromere plays a crucial role during cell division as it is the attachment point for spindle fibers, which help separate the chromatids into the daughter cells.

5. **Conclusion**: Therefore, centromeres are defined as the constricted region of chromosomes where sister chromatids are held together.

**Final Answer**: Centromeres are the constricted region of chromosomes.

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