when these isotopes were used to label cells before viral infection rather than during the process of viral propagation , the saline-soluble dna from infected cells had a specific activity of 10 to 20 per cent less than that of uninfected cells , indicating that the saline-soluble dna was synthesized both from prelabeled precursors of the cell pools and unlabeled materials from the medium .
C0007634
cells
C0018956
precursors