DNA repair

[Sir Gillies]

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Hi guys,

I am struggling to thoroughly understand the difference in DNA repair listed in FA and Kaplan LN. Specifically nucleotide excision repair vs mismatch repair, since it appears that both involve nucleotide errors.

Any help would be truly appreciated. Thanks in advance.

 

[sharklasers]

Mismatch repair happens during or right after DNA replication and removes an abnormal base
Nucleotide excision repair happens when you have an abnormally shaped DNA, like thymine dimers
Base excision repair happens due to damage/mutation in a single base, but not associated with replication

I hope that is right, because its how I understood it

 

[thehundredthone]

Nucleotide excision repair takes places in G1 phase, before new DNA is synthesised. It removes damaged bases, e.g. thymine dimers, that form due to UV exposure or other damage.

Mismatch repair takes place in G2 phase, after new DNA is synthesised. It replaces mismatched nucleotides from the new, i.e. unmethylated strand (this methylation of the old DNA is mentioned on pg.68, don't confuse it with hypermethylation) before cells go into the M phase.

Most repair happens in the G1 phase before S phase. Only mismatch repair takes place in G2, to check the quality of the newly synthesised DNA.

Hopefully that clears up the principle you're trying to understand.

 

[dentovis]

All this is for prokaryotes right? Not eukaryotes? When it comes to this chapter are we strictly speaking prokaryotes?

 

[thehundredthone]

No, this is for eukaryotes (also?). NER defects cause xeroderma pigmentosum and mismatch repair defects cause HNPCC.