“Researchers have completed the genetic sequences of two types of cancer — skin cancer and small-cell lung cancer — revealing that the genomes bear the hallmarks of their respective carcinogens: sun and smoke. Worldwide, the two diseases kill a total of nearly 250,000 people each year, despite the fact that they are largely preventable. Tumours develop when a normal cell’s DNA is damaged, allowing that cell to proliferate unchecked. By sequencing and cataloguing all the mutations in a single tumour type from multiple individuals, scientists aim to identify the genes that are most susceptible to damage, to understand the processes underlying DNA repair, and to develop drugs that counteract certain types of damage… Peter Campbell, a haemotologist and cancer-genomics expert at the Sanger Institute who worked on the latest studies, says that the number of genetic mutations they identified — 33,345 for melanoma and 22,910 for lung cancer — was remarkable. The mutations were not distributed evenly throughout the genome — many were present outside of gene-coding regions, suggesting that cells had repaired damaged DNA in those key regions.”