DNA polymerase direction

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sagda
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DNA polymerase direction

Post by sagda » Sat Oct 31, 2009 2:15 pm

Why do DNA polymerases elongate chains in the 5' to 3' direction only ? why not from 3' to 5' ?

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mith
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Post by mith » Sat Oct 31, 2009 4:20 pm

try drawing out the elongation process. remember to count the phosphates.
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JackBean
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Post by JackBean » Sun Nov 01, 2009 12:11 am

Try to think about repairing mistakes in both cases ;)
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MrMistery
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Post by MrMistery » Sun Nov 01, 2009 2:07 am

jackbean is right: conceptually it could go the other way, but repair... that's a different story
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sagda
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Re: DNA polymerase direction

Post by sagda » Sat Nov 14, 2009 1:34 pm

I tried to draw it, the 3'-oH of the incoming nucleotide will be added to the primer terminus ( which has a 5'-triphosphate ), then removal of the incorrect 5' terminal triphosphate takes place, and the primer becomes 5' monophosphate....why don't the DNA polymerase continue elongation after that? is this a necessary condition( primer must be triphosphate) for elongation to take place?

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JackBean
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Post by JackBean » Sun Nov 15, 2009 1:10 am

You need to release energy in order to add new nucleotide. So, if you had there monophosphate, you have nothing to hydrolyse and thus you can't add new nucleotide ;)
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