Figure 3.

One-step growth of HAM⁺, HAM^sl, and HAM⁻ cells in HAM medium containing 10% dialyzed serum. Wells containing 10⁴ cells in 1 ml of medium were counted after 4 days of incubation. The thin central vertical line indicates the standard concentration of 5-methyl-dC in HAM medium. In these experiments, the concentration of 5-methyl-dC was sequentially reduced (from 0.5 or 1.0 mg/ml) by 1:3 dilutions. Approximately 100 times less 5-methyl-dC is required by HAM⁺ cells to produce the same amount of growth of HAM⁻ cells.