Which is unique to mitosis and does not occur in meiosis ?

Options

A. Homologous chromosomes cross over
B. Homologous chromosomes pair and form bivalents
C. Homologous chromosomes behave independently
D. Formation of biphasic plate at metaphase

Answer

To determine which feature is unique to mitosis and does not occur in meiosis, we can analyze the characteristics of both processes.

### Step-by-Step Solution:

1. **Understanding Mitosis and Meiosis**:
- Mitosis is known as equational cell division, where the chromosome number remains the same, producing two genetically identical daughter cells.
- Meiosis is known as reductional cell division, where the chromosome number is halved, producing four genetically diverse gametes.

2. **Identifying Unique Features**:
- In mitosis, homologous chromosomes behave independently. This means that during anaphase, the sister chromatids of each chromosome are pulled apart to opposite poles without any pairing or crossing over with homologous chromosomes.
- In meiosis, homologous chromosomes pair up and undergo crossing over, which leads to genetic recombination. This process does not occur in mitosis.

3. **Analyzing Options**:
- **Option 1**: Homologous chromosomes cross over - This occurs in meiosis, not mitosis.
- **Option 2**: Homologous chromosomes pair and form bivalents - This also occurs in meiosis.
- **Option 3**: Homologous chromosomes behave independently - This is true for mitosis and does not happen in meiosis.
- **Option 4**: Formation of a biphasic plate at metaphase - This occurs in both mitosis and meiosis.

4. **Conclusion**:
- The correct answer is that in mitosis, homologous chromosomes behave independently, which is a feature that does not occur in meiosis.

### Final Answer:
**In mitosis, homologous chromosomes behave independently, which does not occur in meiosis.**