Question

Crossing over occurs during

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

Answer 1

The correct option is B Pachytene

The pairing of homologous chromosomes is a defining characteristic of meiosis. Homologous chromosomes pair during prophase stage of meiosis I. The prophase stage of meiosis I have substages, leptotene, zygotene, pachytene, diplotene and diakinesis stages. Crossing over is a physical exchange of equal pieces of adjacent non-sister chromatids. When crossing over occurs, chromatids break and may be reattached to a different homologous chromosome. Crossing over occurs during pachytene stage between non-sister chromatids of a pair of homologous chromosomes.

Thus, the correct answer is Pachytene.