"Not only will the library be a major boost to public sector research, but it will also be extremely valuable within the commercial sector. It has the potential to transform the study of gene function and accelerate drug development."

Scientists from the two charities will use the RNA interference library to create cells in which all genes are fully functional bar one. They will engineer cells with one of the library's DNA vectors “ coding for a specific piece of interference RNA “ in order to permanently block a particular gene. Researchers will study the behaviour of cells in detail and particularly how they respond to losing individual genes.

They will also bombard cancer cells with numerous vectors simultaneously, in order to answer one of the ultimate questions in cancer biology “ what is the genetic basis of a malignant cell? They will screen the treated cells for the handful that have reverted to type and become normal again. The set of genes switched off by RNA interference in these cells may represent the most crucial group of cancer genes in the human genome and are likely to be extremely good targets for future anti-cancer drugs.

Cancer Research UK's Chief Executive, Professor Alex Markham, says: "The word breakthrough is used much too often in connection with science, but the discovery of RNA interference may well justify the term.

"With the completion of this library, our researchers will be able to select any one of 8,000 genes and turn it off, if not at the flick of a switch then certainly with the squeeze of a pipette. "For the first time, we'll be able to quickly and easily dissect out the function of individual genes from the 35,000 in the human genome, which will be of huge benefit in identifying targets for the anti-cancer drugs of the future."