DNA insertion mutations may be caused by the invasion of viruses. A mutation is any spontaneous change that occurs randomly on DNA strand that is passed on to an organism's offspring. They are caused by chemical interactions or radiations . In DNA, the sequence of nucleotides determines how proteins are built, with each segment of three nucleotides encoding a single amino acid. When one nucleotide is inserted into the sequence, the whole sequence shifts, and all the triples are changed, which can cause mutations.