A major step forward in our understanding of how enzymes 'edit' genes has been made by an international team of researchers, paving the way for correcting genetic diseases in patients. Researchers have observed the process by which a class of enzymes called CRISPR -- pronounced 'crisper' -- bind and alter the structure of DNA. The results provide a vital piece of the puzzle if these genome editing tools are ultimately going to be used to correct genetic diseases in humans.