The key event in controlling replication is the behavior of the ORC complex at the origin.

Cdc6 protein is an unstable protein that is synthesized only in G1.

Cdc6 binds to ORC and allows MCM proteins.

Cdc6 binds to ORC and allows MCM proteins to bind.

Cdt1 facilitates MCM loading on origins

TLS Online TPP Program

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#Unit 2. Cellular Organization

A conserved region found in every core histone, called the histone-fold domain HFD.

TLS Online TPP Program

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#Unit 2. Cellular Organization

The histone-fold domain is composed of three a-helical regions separated by two short unstructured loops.

 

TLS Online TPP Program

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#Unit 2. Cellular Organization

Histone-fold domain mediates the assembly of Histone-only Intermediates

TLS Online TPP Program

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#Unit 2. Cellular Organization

H3 and H4 histones first form heterodimers that then come together to form a tetramer with two molecules each of H3 and H4. While H2A and H2B form heterodimers in solution but not tetramers. This assembly without DNA called Histone-only Intermediates 

TLS Online TPP Program

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#Unit 2. Cellular Organization

First the H3.H4 assemble into tetramer (HOI) then DNA wrapped over H3.H4 tetramer. 

TLS Online TPP Program

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#Unit 2. Cellular Organization