It remains to be seen if the DNA changes are permanent. The body can detect and replace damaged or incorrect DNA, and restore the original correct DNA sequences you were born with. Advanced error correction protocol is one of the primary functions of the immune system. Exposure to many forms of radiation, for example, can alter and damage DNA - and if the damage is not too severe, usually the body can find the damaged areas and either replace or repair them. Mutation is when the body fails to detect the change that has occurred, and allows the effects of the change to continue onward. In cases where the DNA has been permanently changed, they are no longer strictly human. They are now mutants.