The two charities have produced the world's first cancer-focussed RNA interference (RNAi) library - a collection of 23,742 probes designed to inactivate a total of 7,914 different human genes.
Hundreds of scientists from both charities will now receive copies of the library, which exploits the unique ability of RNAi to switch off a single one of a cell's 35,000 genes. They will begin the second phase of the initiative: working out what individual genes do by studying how cells are affected by their loss.
Building on the huge success of the Human Genome Project, scientists will use the library to help identify the cluster of genes representing 'the essence of cancer', said the charities in a statement. These genes, crucial for the development of the disease, are likely to be ideal targets for the future generation of anti-cancer drugs.
To ensure that gene inactivation is possible in a range of different conditions and in different types of cells, the scientists have developed three vectors for each gene they are targeting.
The library is claimed to be the world's first to focus on cancer and among the first to use vectors, which allow genes to be switched off more stably than with other systems and for longer periods of time.
Cancer Research UK's Julian Downward, leading the project at the charity's London Research Institute, said that although the entire human genome has been completed, "what we really need to know is what these genes are doing and in particular, which of them are contributing to cancer."
"With our library now completed, we should be able to answer some fundamental questions about the function of our genes and how they work together to produce a healthy cell or a cancerous one."
Cancer Research UK's technology transfer subsidiary, Cancer Research Technology, will license copies of the library to a number of pharmaceutical companies, with the proceeds being ploughed back into the charity's research budget.