Question

Diplotene stage of Prophase – I is characterised by
A) Dissolution of synaptonemal complex.
B) Separation of synapsed homologous chromosomes except at the site of crossovers.
C) Formation of X-shaped structures called chiasmata.
D) All of these.

Answer 1

Hint: The process where a single cell undergoes division (twice) to result in the production of four new cells containing half of the original genetic information stored within the parent cell is known as meiosis.

Complete Answer:
Stages in meiosis I are as follows –
- Prophase I: The chromosomes undergo condensation and simultaneously pairing up. Every single chromosome carefully aligns itself juxtaposed to its homologous partner so that both of them match up at their corresponding ends. This results in formation of an X-shaped structure known as Chiasmata and the process is known as crossing over.
- Metaphase I: The homologous pair lines up at the site of the metaphase plate to undergo separation. This time, the orientation of each pair is randomized.
- Anaphase I: Both the partners of the homologous chromosome pair are pulled apart and start migrating towards the opposite ends.
- Telophase I: Finally, the separated chromosomes arrive at the respective poles featuring reformation of the nuclear membrane and decondensation of the chromosomes.

Option A: During the diplotene phase of Prophase I, the synaptonemal complex undergoes dissolution. Thus, this is a correct option for the given question.
Option B: The synapsed homologous chromosome undergoes separation at the crossing over site. Thus, this is also a correct option for the given question.
Option C: The homologous pairing of the chromosomes results in the formation of an X-shaped structure known as chiasmata. Thus, this is even a correct option.
Option D: As all the statements are correct, therefore, this is the correct option.

Thus, the Option D) All of the above is the correct option.

Note: In Meiosis I, the homologous pair of chromosomes separates during the first round of cellular division itself while in Meiosis II, sister chromatids undergo a separation.