The causes of mutations
Mutations happen for several reasons.
- 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. That small
difference from the original DNA sequence is a mutation.
To download this image, right-click (Windows) or control-click (Mac) on the image and select "Save image."
External influences can create mutations
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. So the cell would end up with DNA slightly different than the
original DNA and hence, a mutation.