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T4 DNA polymerisation - elongation or removal? (Nov/08/2009 )

Dear all,

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

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 ?

Or ?


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).