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Old 06-20-2012
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Default DNA repair - G1 or/and G2?

Kaplan:
"G2 phase - Replicated DNA is checked for any errors before cell division."

Goljan says that:
cell is temporally arrested and its DNA is checked for any errors in G1 phase - that is how p53 works.
Goljan emphasized that it is crucial to check DNA for any errors before (!) the cell goes into S phase - which to me totally makes sense.

So do we have DNA checked in both G1 and G2 or one of the above sources in wrong?
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Old 06-20-2012
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Hi,
From my knowledge p53 works mainly in the transition point G1/S and arrests the cell at that point and can even induce apoptosis, it's logic that it will only work in G1/S phase, because a cell that is entering the cell cycle from G1 to S could have been found on G0 before and alot of mistakes might have been accumulated so it needs time till he repairs all of them so p53 arrests the cycle, on the other hand when cell goes through S he is devoted to complete the cycle and G2 is very short phase and the only mistakes that could have happened to the DNA are mismatches during replication, but becuase the new strand that is formed is not methylated that mistakes are recognized on the new strands and repaired by the mismatch repair method MSH2,MLH1, so p53 is really not needed. Always remember that p53 and all this other methods of stopping cycle all require energy and our cells are much more beneficial from us in saving energy sources, at least in my opinion.
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Quote:
Originally Posted by Casandra View Post
Kaplan:
"G2 phase - Replicated DNA is checked for any errors before cell division."

Goljan says that:
cell is temporally arrested and its DNA is checked for any errors in G1 phase - that is how p53 works.
Goljan emphasized that it is crucial to check DNA for any errors before (!) the cell goes into S phase - which to me totally makes sense.

So do we have DNA checked in both G1 and G2 or one of the above sources in wrong?
Yes there are DNA check in both G1 and G2

-Rb and p53 check at G1 before progression to S-phase
-hMLH1 and hMSH2 check at G2 phase.

mutation of Rb cause retinoblastoma/osteosarcoma while p53 mutation results to most human cancers.
mutation of either hMLH1 or hMSH2 in G2 causes lynch syndrome/HNPCC
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