Mutations can also be caused by exposure to specific chemicals or radiation. These agents cause the DNA to break down. This is not necessarily unnatural  even in the most isolated and pristine environments, DNA breaks down. Nevertheless, when the cell repairs the DNA, it might not do a perfect job of the repair.he causes of mutations. 1. DNA fails to copy accurately. Most of the mutations that we think matter to evolution are naturally-occurring.. For example, when a cell divides, it makes a copy of its DNA  and sometimes the copy is not quite perfect.