Mutations

A mutation is a change in the gene structure of an organism.

Background
Mutations can occur naturally, or from exposure to external nuclear and biochemical agents. They may also be created artificially through genetic manipulation. Radiation as a nuclear agent affects both flora and fauna, and can be a major catalyst in the creation of new mutations in humans. Ghouls inherently develop a resistance to radiation during their mutation, with feral ghoul reavers and glowing ones becoming capable of emitting radiation themselves.

A common effect of radiation-induced mutations in animals and plants is their increased size, as can be seen in bloatflies, bloodbugs, geckos, giant ants, mirelurks, mole rats, and radscorpions. Another result can be the growth of additional body parts, as seen on brahmin.

Behind the scenes
According to the Fallout Bible, widespread mutations in animals and humans, caused by the Forced Evolutionary Virus, were seen by the year 2080.