Question

Recombination occurs during _______ stage of meiosis-I.

• A. leptotene
• B. pachytene
• C. zygotene
• D. diplotene

Answer 1

The correct option is B pachytene

The prophase of meiosis I is divided into five stages: leptotene, zygotene, pachytene, diplotene, diakinesis. Leptotene stage marks the arrangement of chromatin fibres into thin, long strands. During the zygotene stage the synapsis of homologous chromosomes takes place, along with the formation of synaptonemal complexes. Pachytene marks the recombination of genes and crossing over. Diplotene is marked by the formation of chiasma. Terminalisation of chiasmata occurs in diakinesis.
In the pachytene stage, the process of exchange of fragments of non-sister chromatids of homologous chromosomes occurs. The process is referred to as recombination. It is during this process that there is a tendency of the genes on the same chromosome to get separated provided they are distantly located.