Chiasmata are formed during (1 Zygotene (2) Pachytene (3) Diplotene (4) Leptotene

Answer: (3)

During diplotene, the paired chromosomes form an X-shaped structure known as chiasmata. At chiasmata, the crossing over between two non-sister chromatids takes place.

Zygotene – Here the chromosomes start pairing and synapsis between homologous chromosomes begins.

Pachytene – Here, the synapse is formed, by a chromatid of one pair attaching to the chromatid in a homologous chromosome and the crossing over begins.

Leptotene – The chromosomes start to condense and attach to the cell membrane through a ‘cap’ like structure at the end of chromosomes called telomeres.

Diplotene – Here, the paired chromosomes start to separate from each other into two pairs of chromatids. The synapsis stops with the disintegration of the synaptonemal complex. The homologous pairs of chromosomes remain attached at Chiasma. The chromosomes begin to coil, making the Chiasma very evident under the microscope.

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