Induced mutations on the molecular level can be caused by:

* Chemicals
o Hydroxylamine NH2OH
o Base analogs (e.g. BrdU)
o Alkylating agents (e.g. N-ethyl-N-nitrosourea) These agents can mutate both replicating and non-replicating DNA. In contrast, a base analog can only mutate the DNA when the analog is incorporated in replicating the DNA. Each of these classes of chemical mutagens has certain effects that then lead to transitions, transversions, or deletions.
o Agents that form DNA adducts (e.g. ochratoxin A metabolites)[5]
o DNA intercalating agents (e.g. ethidium bromide)
o DNA crosslinkers
o Oxidative damage
o Nitrous acid converts amine groups on A and C to diazo groups, altering their hydrogen bonding patterns which leads to incorrect base pairing during replication.
* Radiation
o Ultraviolet radiation (nonionizing radiation). Two nucleotide bases in DNA – cytosine and thymine – are most vulnerable to radiation that can change their properties. UV light can induce adjacent thymine bases in a DNA strand to pair with each other, as a bulky dimer.
o Ionizing radiation
* Viral infections[6]