MODEL RELEASED. Cancer research. Researcher sequencing the single nucleotide polymorphisms (SNPs) of cancer cells. SNPs are single nucleotide variations in a DNA sequence. For a variation to be a SNP it must occur in at least 1% of the population. When searching for genes involved in cancer, it is much quicker to search for known SNPs than to search for whole gene sequences. Studying the genetic basis of cancer can lead to the discovery of targets for anti-cancer (chemotherapy) drugs. Photographed at the Northern Institute for Cancer Research, University of Newcastle Upon Tyne, UK.