denaturing gradient gel electrophoresis


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denaturing gradient gel electrophoresis (DGGE)

electrophoretic technique for separating DNA molecules on the basis of their sequence. A gradient of increasingly denaturing conditions, using a chemical denaturant such as formamide or urea, is applied across a gel and as double-stranded DNA molecules migrate through the gel, they denature into partially and then fully single-stranded DNA, with a consequent change in electrophoretic mobility, which dictates their final position in the gel.

The stability of the DNA helix to denaturation depends on the G+C content of the molecule. Thus DNA molecules of similar size, but different %G+C will denature and separate at different denaturant concentrations. The general principle of this technique can be applied to separate HETERODUPLEXES from HOMODUPLEXES based on the degree of COMPLEMENTARY BASE PAIRING between the two strands in each molecule.

A variation of this technique, temperature/ thermal gradient gel electrophoresis (TGGE), employs a temperature gradient, rather than chemical denaturants.