Question

The study of chromosomes at meiotic diplotene shows that:

• A. The intimately paired chromosomes completely separate from each other
• B. The pairing of homologous chromosomes which had initiated in the earlier stage is completed
• C. The homologous chromosomes remain united by chiasmata
• D. None of the above

Answer 1

The correct option is A

Explanation of the correct answer:

1. Diplotene marks the dissolution of the synaptonemal complex and separation of the homologous chromosomes of the bivalents except at the sites of cross-over.
2. The X-shaped structures formed during separation are known as chiasmata.
3. Therefore, the homologous chromosomes remain united by chiasmata.

Explanation of the incorrect answers:

Option B:

1. Diakinesis is marked by the termination of chiasmata and assembly of the meiotic spindle to separate the homologous chromosomes.
2. At this stage, the intimately paired chromosomes completely separate from each other.

Option C:

1. In zygotene, the pairing of homologous chromosomes starts a process known as chromosomal synapsis, accompanied by the formation of a complex structure called synaptonemal complex.
2. A pair of synapsed homologous chromosome forms a complex known as bivalent or tetrad.
3. So, pairing occurs at zygotene stage.

Option D:

1. The option is invalid.
2. The chiasmata formation occurs at diplotene.

Final answer: The study of chromosomes at meiotic diplotene shows that the homologous chromosomes remain united by chiasmata.