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Competition between the wild-type sequence and the 179-member purine PPT pool predominant sequence. The predominant sequence differed from the wild-type sequence at positions −4 and −9. Sequences of PCR-amplified PPT regions of unintegrated viral DNA harvested from Rat2 cells infected with competition virus from passages 1 through 4 were determined. The position of the core PPT is indicated on the left.
