DNA replication

What proteins form the replication forks?

DnaA, DnaB-DnaC

Clamp loader

Sits in the middle, just behind DNA helicase, organising the clamps

What are the 4 main steps of DNA replication?

1. Separation

2. Initiation

3. Elongation

4. Termination

Where does DNA replication begin?

At the origin of replication (OriC in prokaryotes)

What is the function of DnaA?

Binds to OriC to initiate DNA unwinding.

What is the function of DnaB

Helicase that unwinds the DNA helix using ATP

What is the function of DnaC

Helps load DnaB onto DNA

What does DNA Primase (DnaG) do?

Synthesizes RNA primers for DNA polymerase to begin replication.

What does DNA polymerase do?

Adds nucleotides to synthesise the new DNA strand in the 5’ to 3’ direction.

DNA ligase

Joins Okazaki fragments on the lagging strand

Role of SSBP’s

Prevent reformation of double helix in ss regions.

Function of DNA Gyrase (topoisomerase)

Relieves torsional stress by introducing negative supercoils

Why is replication accuracy important?

Errors can change protein shape, function, expression, potentially causing disease.

What mechanisms help ensure replication fidelity?

Bp rules and proofreading by DNA polymerases

Synonymous mutation

A base change that does not alter the a.a sequence of a protein.

What is the role of a sliding clamp?

Keeps DNA polymerase attached to the DNA template