Figure 4.

Schematic depiction of mutation accumulation in a tissue, including expansion into clones. De novo mutations are in black. Mutations can be clonally amplified due to genetic drift or a survival advantage. This is indicated by the two red asterisks in the orange cells. Additional mutations (in black) can subsequently accumulate but all cells will retain the two original mutations in the ancestor cell. The best example of such somatic evolution, but by no means the only one, is the generation of tumors.