Question

Arrange the following events of meiosis in the correct sequence.
1. Terminalization
2. Crossing over
3. Synapsis
4. Disjunction of genomes

• A. 4, 3, 2, 1
• B. 3, 2, 4, 1
• C. 2, 1, 4, 3
• D. 1, 4, 3, 2

Answer 1

The correct option is B 3, 2, 4, 1

During zygoetene stage of prophase I of meiosis I, the homologous chromosomes pair up in a process known as synapsis. At this stage they form a bivalent.
The next stage is pachytene, during which each chromosome of a bivalent forms a duplicate sister chromatid and appears as a tetrad. Exchange of chromatid segments occurs at a point called chiasma between the non-sister chromatids of a tetrad. This is known as crossing over.
The synaptonemal complex holding the homologous chromosomes together dissolves and the homologous chromosomes uncoil and start separating. This is known as disjunction.
But, the non-sister chromatids still remain in contact at the chiasma. Simultaneously, the chromosomes continue to condense and become shorter and the chiasmata moves away from the centromeres and approaches the ends. This process is called terminalisation.

The correct sequence is:
Synapsis $\to$ Crossing over $\to$ Disjunction of genomes $\to$ Terminalization