Figure 1. Models of aging pathways. (A) A scenario in which DNA damage acts as a causal trigger for aging. (B) A scenario in which chromatin structure acts as a causal trigger for aging. Feedback loops, which are likely to exist between most individual events, are not shown for simplicity. (C) Chromatin structure and DNA damage pathways act in an integrated fashion with a multitude of other cellular process to form a network of aging processes.