Arrange the following events of meiosis in correct sequence
(a) Crossing over
(b) Synapsis
`(c)`Terminalisation of chiasmata
(d) Disappearance of nucleolus.

Options

A. b,a,d,c
B. b,a,c,d
C. a,b,c,d
D. b,c,d,a

Answer

To arrange the events of meiosis in the correct sequence, we need to understand the stages of meiosis and the specific events that occur during those stages. Here’s the step-by-step solution:

1. **Synapsis (b)**: This is the first event that occurs during meiosis. It takes place during prophase I of meiosis, where homologous chromosomes pair up closely along their lengths.

2. **Crossing Over (a)**: Following synapsis, crossing over occurs. This is also part of prophase I, specifically during the pachytene stage, where segments of DNA are exchanged between homologous chromosomes, leading to genetic variation.

3. **Terminalisation of Chiasmata (c)**: After crossing over, the next event is the terminalisation of chiasmata. This occurs towards the end of prophase I, where the points of crossing over become visible as chiasmata and move toward the ends of the chromosomes.

4. **Disappearance of Nucleolus (d)**: Finally, the disappearance of the nucleolus occurs at the end of prophase I, signaling the transition into metaphase I.

Putting these events in order, we have:
- **(b) Synapsis**
- **(a) Crossing Over**
- **(c) Terminalisation of Chiasmata**
- **(d) Disappearance of Nucleolus**

Thus, the correct sequence is **B, A, C, D**.