T4 DNA polymerisation - elongation or removal? (Nov/08/2009 )
I have the following question.
I was reading my text book on genetics and found the following sentence:
T4 polymerase will either elongate or remove nucleotides and this depends on avaibility.
What does this mean?
Example lets say we have
5' TTAGCGGAA 3'
3' AARCGCCTT TTAAGGCC 5'
and we add T4 polymerase and some dNTP's , what will happen then?
I suppose the T4 will add thise nucleotides ? untill the template is completed?
But what do they then mean with "remove nucleotide" ?
Do they mean that, by example after adding the first AATTCC it is possible that T4 will remove the last 2 CC because there arent enough GG present to finish the AATTCC ?
So instead of adding 2 GG it would remove the addes CC again ?
With the dNTPs it would fill in the whole sequence... without it would act as an endonuclease and remove the overhanging sequence.
Ok, I see.
So it all depends on how much dNTP's you add.
Is there a limit? I mean: if you add a few ? will it then add or remove nucleotides?
Sorry, don't know the answer to that. I am not even sure what would happen if you left out one of the dNTPs (e.g. just added A, T and C).