... used in the protocol for the analysis of theS-phase checkpoint control. 3. Human fibroblasts GM847 and GM847/ATRkd are used for illustrating radia-tion-dose-dependent G2-checkpoint control. GM847 ... Mammalian Cell Cycle 2323From: Methods in Molecular Biology, vol. 241: Cell Cycle Checkpoint Control ProtocolsEdited by: H. B. Lieberman © Humana Press Inc., Totowa, NJ4Analysis of the Mammalian ... of ATR in doxy-cycline-free medium. GM847 lacks the G1-checkpoint control, and GM847/ATRkd are deficient in G2-checkpoint control (9).2.2. Media, Reagents, and Solutions2.2.1. Cell Culture...