Six possible mutagens are:
1. Reactive chemicals (reactive oxygen species, bromine, benzene, alkaloid…)
2. Physical mutagens (radiation like X rays or ultraviolet radiation, radioactive elements like ¹⁴C)
3. Metals (arsenic, cadmium, chromium, nickel…)
4. Intercalating agents (ethidium bromide)
5. Base analogues
6. Biological mutagens (viruses, bacteria, transposons)