Taq polymerase trivia

Dr. Duncan Clark Duncan at nospam.demon.co.uk
Mon Nov 22 04:34:39 EST 1999

In article <38387B68.DCED1435 at med.unc.edu>, Stephen Snowdy
<stephen_snowdy at med.unc.edu> writes
>Does anyone know why (as if it had a reason) Taq Pol adds an adenine on
>the end of PCR products (as opposed to Pfu which generates blunt-ended
>products).  Got asked this one at a committee meeting and I have no

It's not just Taq that has this terminal transferase activity. 

Klenow has as well. Look for a paper maybe 1987 by Catherine Joyce. You
will find some PAGE gel photos showing the extra base addition.

The single base does not have to be an adenine. It can be any of the
other three bases but is primarily an adenine. One can moderate the
amount of adenine addition by the sequence of the primer (Biotechniques
vol 20 No. 6, pp1004-1010). In short non-template addition adjacent to a
3' terminal C is favoured and that addition adjacent to a 3' terminal A
is not. 

Finally placing the sequence GTTTCTT on the 5' end of primers results in
nearly 100% adenylation of the 3' terminal base - "PIG-tailing". 

The problem with being on the cutting edge is that you occasionally get 
sliced from time to time....

Duncan Clark
DNAmp Ltd.
Tel: +44(0)1252376288
FAX: +44(0)8701640382

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