Figure 2. An AP site blocks Taq-mediated primer extension.
Taq polymerase extension reactions were performed as described in the text on 40-mer oligonucleotides containing either an 8-oxo dG residue (8oxo) or an AP site (AP), see methods section for details, in the absence (-) or presence (+) of complementary primer Z (15-mer, see methods). The products were resolved by electrophoresis, stained with ethidium bromide and subject to scanning densitometry. The relative amount of full-length product (40 nt) was quantitated using image J and plotted on the y axis (arbitrary units).