Question

The cell is said to have entered a stage called as ..........., when synapsis is complete all along the chromosome,

• A. Zygotene
• B. Pachytene
• C. Diplotene
• D. Diakinesis

Answer 1

The correct option is C Diplotene

When synapsis is complete all along the chromosome, the cell is said to have entered a stage called Diplotene. In Pachytene stage, the exchange of information between the non-sister chromatids results in a recombination of information; each chromosome has the complete set of information it had before, and there are no gaps formed as a result of the process. Because the chromosomes cannot be distinguished in the synaptonemal complex, the actual act of crossing over is not perceivable through the microscope, and chiasmata are not visible until the next stage when the synapsis is complete the next stage, that is, Diplotene stage starts.

Here, the synaptonemal complex degrades and homologous chromosomes separate from one another a little. The chromosomes themselves uncoil a bit, allowing some transcription of DNA. However, the homologous chromosomes of each bivalent remain tightly bound at chiasmata, the regions where crossing over occurred. The chiasmata remain on the chromosomes until they are severed at the transition to anaphase I.