Exonuclease activities of DNA Polymerases
An exonuclese is
an enzyme that removes nucleotides. Most DNA
Polymerases, whose primary function is to add
nucleotides in the 5'3'
direction, also have exonuclease activities. (A)
3'-5' exonuclease activity
performs a 'proof reading' function by removing a
nucleotide that has just been added incorrectly. (B)
5'-3' exonuclease activity
displaces nucleotides ahead of the addition by
polymerase activity: this is used for example in
removing RNA primers.
Figure © 2012 TA Brown, Introduction
to Genetics (1st ed.); additional
text © 2014 by Steven M. Carr