Treatment of the enzyme DNA polymerase 1 with subtilism produces two cleavage products, a small fragment which is unstable and a large fragment, called the Klenow fragment, which retains both the 5′-3′ polymerase and the 3′ exonuclease activities, but not the 5′ exonuclease activity, of the intact enzyme, together with the pyrophosphorolysis and pyrophosphate exchange activities. Used to synthesize DNA complementary to single-stranded DNA template by adding nucleotides to the free 3′-hydroxyl end of an annealed DNA primer.

Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.