abstract accumulation of gene changes and chromosomal instability in response to cellular dna damage lead to cancer. dna damage induces cell cycle checkpoints pathways. checkpoints regulate dna replication and cell cycle progression, chromatin restructuring, and apoptosis. checkpoint kinase 2 (chk2) is activated in response to dna lesions. atm phosphorylate chk2. the activated chk2 kinase can p...