The pairing of homologous chromosomes takes place in zygotene phase. A pair of synapsed homologous chromosome forms a complex known as bivalent or tetrad. The point at which the arms of the non-sister chromatids of a pair of homologous chromosomes cross each other are called chiasmata. The chromatids break down at the site of attachment and the exchange of genetic material or a segment of non-sister chromatids takes place between the pair of homologous chromosomes. The process is called crossing over that takes place in the pachytene phase.

Differentiate between the following- G 1 and G 2 phase

Feature G 1 phase G 2 phase Changes in the nucleus It is the post mitotic gap phase. The synthesis of RNA and proteins takes place in G 1 phase. It is the pre mitotic gap phase. The synthesis of RNA and proteins continues but the synthesis of DNA stops in G 2 phase. It come after S phase.