Deletions are mutations<span> in which a section of DNA is lost, or deleted. Since protein-coding DNA is divided into codons </span>three<span> bases long, insertions and deletions can alter a gene so that its message is no longer correctly parsed. These changes are called frameshifts.</span>
Restriction enzymes are DNA-cutting enzymes found in bacteria (and harvested from them for use). Because they cut within the molecule, they are often called restriction endonucleases.