Nobel laureate Francis Crick, who half a century ago with James Watson made one of the seminal discoveries of modern science, the double-helix structure of DNA, died Wednesday in San Diego. He was 88 years old.

Crick died at San Diego’s Thornton Hospital after a long battle with colon cancer. He remained actively involved in theoretical research until just before his death.

Crick’s 1953 discovery with Watson almost single-handedly launched the modern field of molecular genetics, with far-reaching implications for fathoming our biology as well as practical spin-offs ranging from genetic engineering to DNA fingerprinting.

Crick’s later work was central in cracking the genetic code: how stretches of DNA carry the instructions for all the structures of life.

Fascinated by the biology of the brain from an early age, Crick devoted the final portion of his life to tackling the science of consciousness, a mystery he described as “the major unsolved problem in biology.”

Colleagues and friends remembered him as an endlessly curious man with a first-class intellect who never tired of discussing ideas and who had a keen homing instinct for the most important scientific mysteries of the day.

“He was the living incarnation of what it is to be a scholar: brilliant, rational, dispassionate, and always willing to revise his own opinions and views in light of the actions of a universe that never ceased to astonish him,” said Professor Christof Koch of the California Institute of Technology, Crick’s collaborator for many years. “He was editing a manuscript on his death bed, a scientist until the bitter end.”

An inveterate collaborator and gatherer of thinkers about him, Crick mused over the years on questions as varied as why people dream, where life came from and whether much of the DNA in our cells is parasitic junk.

“Until his death, Francis was the person with whom I could most easily talk about ideas,” Watson, now chancellor of the Cold Spring Harbor Laboratory on Long Island, N.Y., said in a statement Thursday. “He will be sorely missed.”