Question
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Exchange of genetic material takes place during _______
(a)diplotene
(b)leptotene
(c)zygotene
(d)pachytene

Answer
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Hint It is the third stage of meiosis prophase-1 (a five-stage process). It has gone before by the zygotene stage, where synapsis, for example blending of homologous chromosomes occurred. Due to synapsis becoming distinct, the tetrad formed and four chromatids became clearly visible. There are four kinetochores present in each tetrad.

Complete answer
A-Diplotene–The condensation of chromosomes takes place when the synaptonemal complex disappears.
B.Leptotene – Chromosomes are more clearly visible.
C.Zygotene – Synapsis takes place.
D. Pachytene –crossing over occurs, the exchange of genetic material takes place.

Additional information
In this process, there is an exchange of genetic material between non-sister chromatids of homologous chromosomes. There are rearrangement and reshuffling of the genetic material of two parental homologous chromosomes. It is an enzyme-mediated process. Recombinase is the enzyme involved in crossing over.
Recombination nodules show up and homologous chromosomes are connected to one another at the site of the traverse.
During the diplotene process, recombination is accompanied by the formation of chiasmata, which appear in the next stage.
Possibly, meiosis can yield entirely suitable items if the chiasmata are bound to areas distal to (i.e., further from the centromere than) the trade focuses.

So the correct answer is ‘pachytene’.

Note: The long pachytene stage begins with the completion of synapsis and is associated with further thickening and shortening of chromosomes. During this stage, trades of chromosome material among maternal and fatherly homologous chromosomes happen by traverse. Contingent upon the chiasmata, various parts of the chromosomes can be noticed. Atomic and cytoplasmic development of pachytene spermatocytes brings about these phones turning into the bigger of all germ cells.