Question

What are the two mechanisms involved in sister cohesion?

Answer 1

Sister chromatid cohesion:

1. In the S-phase (synthesis phase) when the DNA gets replicated, this process is linked to the separation of sister chromatids in mitosis by sister chromatid cohesion.
2. A protein complex called cohesion holds the replicated sister chromatids together after their synthesis

The mechanism involved in sister cohesion are:

1. DNA catenation
2. Protein complex (cohesion)

DNA catenation:

1. It is the large interweaving of the replicated DNA, which occurs when the two replication forks come close to each other, during DNA replication.
2. The topoisomerase enzyme II removes most of the part of this catenation so that it makes only a minor contribution to cohesion during metaphase.

Protein complex (cohesion) :

1. Cohesin is the complex of proteins that associates with the replicated DNA molecules.
2. These protein complexes hold the sister chromatids together in metaphase, and their removal is the important event in sister chromatid separation at the transition of metaphase to anaphase.