A WAY of editing the genetic code one letter at a time has been developed that could help scientists conquer diseases caused by tiny glitches in DNA.

The process allows single letter mutations not only to be introduced to cells but accurately identified.

Using the technique, researchers were able to spot one mutant in a sample of 1000 cells.

The research raises the prospect of accurately modelling human diseases in the laboratory, as well as finding cures that fix specific disease mutations.

"Our method provides a novel way to capture and amplify specific mutations that are normally exceedingly rare," said lead scientist Dr Bruce Conklin, from the Gladstone Institutes in California, US.

The human genetic code, written in DNA, is made up of repeating sequences of four chemical "building blocks" designated by the letters A, C, T and G. Substituting just one letter for another can lead to devastating diseases.

"Our high-efficiency, high-fidelity method could very well be the basis for the next phase of human genetics research," said Dr Conklin.