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 event is unique to mitosis and does not occur in meiosis, we can analyze the options provided:

1. **Homologous chromosomes crossing over**: This process occurs during meiosis, specifically in Meiosis I, where homologous chromosomes exchange genetic material. Therefore, this option is incorrect.

2. **Homologous chromosomes pair and form bivalents**: This pairing also occurs during Meiosis I, where homologous chromosomes align and form structures known as bivalents. Thus, this option is also incorrect.

3. **Homologous chromosomes behave independently**: In mitosis, homologous chromosomes do not pair up; instead, they behave independently during the separation process. This characteristic is unique to mitosis and does not occur in meiosis, where homologous chromosomes do pair and segregate together. Therefore, this option is correct.

4. **Formation of the metaphase plate at metaphase**: While the metaphase plate does form during both mitosis and meiosis, it is not unique to mitosis. Hence, this option is also incorrect.

Based on the analysis, the correct answer is:
**Homologous chromosomes behave independently.**