Figure 5.

Synchronization of cells for in vivo repair assays. Normal human fibroblasts (GM 38A) were grown to confluency in media containing 10 mM hydroxyurea and incubated for 0 h (A, +UV; B, −UV), 8 h (C, +UV; D, −UV), 24 h (E, +UV; F, −UV), and 48 h (G, +UV; H, −UV) at 37°C in 5% CO₂ incubators. The cells were then harvested and treated with 70% ethanol and 100 μg/ml RNAse A. The DNA content of the cells was measured by flow cytometry.