KRAS and neoplasm: Two sets of controls were used for comparison: embryos injected with only KRASG12D and un-stimulated embryos expressing the oncogene and either Arch or ChR2D156A (light by itself does not affect Vmem of cells that do not express light-gated channels, and tumor incidence does not vary among KRAS-only injected embryos kept in dark, ambient light, or blue/red optogenetic exposure [data not shown]).