Answer:

Explanation:

changes a CELL undergoes during the following stages are −

Leptotene

Also CALLED thin-threaded stage.

Volume of nucleus increases.

Formation of aster.

Condensation of nuclear chromatin by dehydration.

Chromosome appears long thread like and made of two sister chromatids.

Thin-threaded Stage

Zygotene

Also called yoked-threaded stage.

Pairing of homologous chromosomes occurs. This is called SYNAPSIS or syndesis.

Formation of bivalents.

Pairing of homologous chromosomes in a zipper-fashion.

Yoked-threaded Stage

Pachytene

Also called thick-threaded stage.

Further condensation of chromosomes.

Sister chromatids are visible which are joined at the centromere and is known as dyad.

Crossing over occurs between two non-sister chromatids of homologous chromosomes.

Crossing over is REGULATED by recombinase enzyme.

Thick-threaded Stage

Diplotene

Called double threaded stage.

Longest duration.

Nuclear membrane and nucleoli start disappearing.

The homologous chromosomes start separating.

The point of attachment or crossing over is known as chiasmata.

The chiasmata starts MOVING towards the ends of chromosomes called terminalisation.

Double-threaded Stage

Diakinesis

Terminalisation is completed.

The non-sister chromatids remain in contact with each other at the telomeres.

Complete disappearance of nuclear membrane and nucleoli.

Diakinesis