In a boost to cancer research, Princeton scientists have invented a fast and reliable method for identifying alterations to chromosomes that occur when cells become malignant. The technique helps to show how cells modify their own genetic makeup and may allow cancer treatments to be tailored more precisely to a patient’s disease.Cancer cells are known among biologists for their remarkable ability to disable some genes and overuse others, allowing their unchecked growth into tumors. The most aggressive of these distortions occurs when cells delete or multiply chunks of their own chromosomes. Cells can simply snip strings of genes from the chromosome, or make many extra copies of the string and reinsert them into the chromosome. Until now, scientists had no routine way to detect these alterations except for very large-scale deletions or additions. Finding small, but critical additions or deletions required painstaking, gene-by-gene searches. Combining computer science and biology, Princeton scientist Olga Troyanskaya, graduate student Chad Myers and other colleagues invented a method for quickly analyzing an entire genome -- all the genes contained in a cell -- and producing a reliable list of chromosome sections that have been either deleted or added.