NEW YORK, Apr 12: The Nobel Prize medal won by Francis Crick, the co-discoverer of DNA, sold for 2.27 million dollars at auction yesterday, a day after a letter in which Crick outlined the achievement to his young son became the most expensive letter ever auctioned when it fetched more than $6 million. Crick, working with James Watson, unraveled the double-helix structure and function of deoxyribonucleic acid (DNA) in Cambridge, England. They won the Nobel Prize in medicine in 1962 for their ground-breaking work. (agencies)