Which of the following not occurs in Anaphase -1

Options

A. Segregation of homologous chromosomes
B. Shortening in spindle
C. Poleward movement of chromosomes
D. Division of centromere

Answer

To determine which event does not occur in Anaphase I, we will analyze the options provided based on our understanding of the cell cycle, specifically focusing on the events of Anaphase I of meiosis.

### Step-by-Step Solution:

1. **Understanding Anaphase I**:
- Anaphase I is a stage in meiosis where homologous chromosomes are separated and pulled towards opposite poles of the cell. This is crucial for reducing the chromosome number by half in the resulting gametes.

2. **Analyzing the Options**:
- **Option 1: Segregation of the homologous chromosomes**:
- This occurs in Anaphase I as homologous chromosomes are separated and move towards opposite poles.
- **Conclusion**: This event occurs in Anaphase I.

- **Option 2: Shortening of the spindle fibers**:
- During Anaphase I, as the chromosomes are pulled apart, the spindle fibers shorten to facilitate this movement.
- **Conclusion**: This event occurs in Anaphase I.

- **Option 3: Poleward movement of the chromosomes**:
- The chromosomes indeed move towards the poles during Anaphase I. This is a key characteristic of this phase.
- **Conclusion**: This event occurs in Anaphase I.

- **Option 4: Division of centromere**:
- The division of the centromere occurs in Anaphase II of meiosis, not Anaphase I. In Anaphase I, the centromeres remain intact as the homologous chromosomes are separated.
- **Conclusion**: This event does not occur in Anaphase I.

3. **Final Answer**:
- The event that does not occur in Anaphase I is **Option 4: Division of centromere**.