Tributes were paid on Wednesday to the British biochemist Frederick Sanger, the "father of genomics" and the only person to win the Nobel Prize for Chemistry twice, following his death at the age of 95.
Sanger first won the prize in 1958 for his work on the structure of proteins, notably insulin, and shared it with two others in 1980 for pioneering developments in DNA sequencing that are still being used today.
He died in his sleep on Tuesday morning at Addenbrooke's Hospital in Cambridge, eastern England, according to a spokesman for the Medical Research Council.
Colleagues described him as an inspiration: a doggedly determined but self-effacing scientist whose contribution to modern genetics and molecular biology is impossible to overstate.
The sequencing of insulin proved of great importance to medicine, but it was his technique to determine the exact sequence of the building blocks in DNA, called bases, that cemented his reputation.
It allowed long stretches of DNA to be rapidly and accurately sequenced and was central to the Human Genome Project's mammoth achievement in mapping more than three billion units of human DNA.
The tributes were led by Professor Mike Stratton, director of the Wellcome Trust Sanger Institute in Cambridge which bears his name and played a major role in the HGP.
"He won two Nobel Prizes, one of only four people to do so," Stratton said.
"His work for his second prize, a method to decode DNA, has transformed our understanding of life on Earth and is the foundation of developments in healthcare from understanding inherited disease to developing new cancer treatment.
"It was an honour for this institute when Fred acceded to founding director John Sulston's request that we be named after him. Fred's only stipulation was that 'It had better be good'."
Sanger received several honours from the British state although he declined a knighthood, saying with typical humility that he would prefer not to be called 'Sir'.
"Fred Sanger was one of the most important scientists of the 20th century," said Craig Venter, founder of the J. Craig Venter Institute in the United States.
"He twice changed the direction of the scientific world: first with the sequencing of insulin, proving that proteins were linear strings of amino acids; and second with his then-new method of sequencing DNA, which led to the field of genomics. His contributions will always be remembered."
Nobel laureate Venki Ramakrishnan said he was "one of the outstanding scientists of the last century" and said his determination to carry out experiments himself right up to the end of his career made him a "superb role model".