FIG. 2.

PCR analysis of plaque isolates. Viral DNA was prepared from plaque isolates and analyzed by PCR using primers B and C (Fig. 1). Samples were either analyzed directly (lanes −) or were adjusted to 5 mM MgCl₂ and digested with 0.5 U of SpeI (lanes +) prior to electrophoresis on a 1.2% agarose gel. pTG3602ΔL1 and pTG3602 indicate amplification from the mutant or wild-type plasmid, respectively. Uninfected, amplification of DNA prepared from uninfected 293-L1 cells. Lane M, 1-kb molecular size marker.