When the cystic fibrosis gene was found in 1989, therapy seemed around the corner. Two decades on, biologists still have a long way to go, finds Helen Pearson. During the day, Lap-Chee Tsui and Francis Collins were attending a gene-mapping workshop. At night they were scrutinizing the pages churning out of a fax machine they had set up in a dorm room. Their hunt for the cause of cystic fibrosis had reached a gene that looked from its sequence like it might have a role in transporting ions through cell membranes, a process that goes awry in those with the...