Chemical and enzymatic cleavage of mismatch (CCM)

As outlined in previous sections, PCR products that contain
point mutations form hybrid molecules with their normal
counterparts known as heteroduplexes. The two DNA strands
in these heteroduplexes are perfectly matched except at the
site of the mutation, where base pairing cannot occur. These
mismatched sites can be recognised both by specific enzymes
and by chemicals such as osmium tetroxide and piperidine,
which cleave the DNA at the site of mismatch. This property
can therefore be used to detect mutations within a PCR
product by polyacrylamide gel electrophoresis to visualise the
cleavage products.