Denaturing gradient gel electrophoresis is a method to identify small mutations (e.g., point mutations). The definition of a point mutation is the transition or transversion of one nucleotide into another. However, there are more types of small mutation such as deletions or insertions of one or more nucleotides that can be identified by DGGE as well.
In fact, these mutations will cause a large difference in melting temperatures in both the homoduplexes and the heteroduplexes and can therefore be seen quite clearly on the gels. As mentioned earlier, DGGE products typically range from 200 to 400 bp, making DGGE well suited for analyzing exons in genomic DNA, although DGGE can be applied to RNA screening as well. However, RNA is more vulnerable to degradation than DNA and requires conversion into complementary (cDNA). Scanning for mutations in genes involved in hereditary disorders is therefore often done on genomic DNA for both diagnostic purposes and for research.
For instance, DGGE is widely applied in the analysis of the various genes involved in hereditary colorectal cancer such as APC, MSH2, MSH6, MLH1, and so forth Presymptomatic diagnosis is particularly important with a potentially lethal disease such as colorectal cancer that can be treated. Mutation analysis has revealed that in families with colorectal cancer, the mutation is often unique. Obviously, screening a family for an unknown mutation requires a technique, such as DGGE, that is tried and proven, particularly when the stakes are very high.
However, for research purposes, reliability is important as well. Investigation into types of mutation requires that the screening will reveal almost all point mutations so that an unbiased analysis of the mutation spectrum can be made.