Multiple subphases of DNA replication in Chinese hamster ovary (CHO-K1) cells.

Replicative DNA synthesis has been measured throughout the S phase in synchronized populations of Chinese hamster ovary cells. When exponentially growing, cells in suspension cultures were subjected to counterflow centrifugal elutriation and the resolution power was increased the biphasic replication profile has been resolved and multiple subphases were distinguished. These replication peaks, termed replication checkpoints, are distributed evenly throughout the S phase. The replication checkpoints have been characterized by their average C values corresponding to 2.05, 2.12, 2.2, 2.45, 2.6, 2.8, 2.95, 3.15, 3.3, 3.45, and 3.85.