Denaturing gradient gel electrophoresis

This method exploits differences in the stability
of DNA segments with and without mutation.
While double-stranded DNA of a control person
is completely complementary (homoduplex), a
mutation leads to a mismatch at the site of mutation
(heteroduplex). This DNA is less stable
than completely complementary DNA strands
(it has a lower melting point). If normal DNA
(control) and DNAwith the mutation are placed
in a gel with an increasing concentration
gradient of formamide (denaturing gradient
gel), the mutant and normal DNA can subsequently
be differentiated in a Southern blot.
The normal DNA remains stable to higher concentrations
of formamide and migrates farther
than mutant DNA, which dissociates earlier and
therefore does not migrate as far.