James Watson, who has died aged 97, was the 25-year-old American biologist who in 1953, with Francis Crick, revealed the double helix structure of DNA, the chemical of which genes are made; for this a...

James D. Watson, whose co-discovery of the twisted-ladder structure of DNA in 1953 helped light the long fuse on a revolution in medicine, crimefighting, genealogy and ethics, has died.

His death, in a hospice, was confirmed on Friday by his son Duncan, who said Dr. Watson was transferred to the hospice from a hospital this week after being treated there for an infection.