In the letter to his 12-year-old son Michael in March 1953, Crick described the discovery that would later bring him a Nobel Prize and included a sketch of the helix shape he and James Watson had determined while at Cambridge University.
In the seven-page letter written more than a month before the pair officially published their work, Crick told his son how he and Watson found the genetic mechanism "by which life comes from life."
The letter, purchased by an anonymous buyer, had been expected to sell for $1 million, the BBC reported Wednesday.
Crick, along with James Watson and Maurice Wilkins, was awarded the 1962 Nobel Prize for Physiology or Medicine for "discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material."
Crick's Nobel medal along with the check and diploma he received as part of the prize will also be up for auction later at Heritage Auctions in New York.
Twenty percent of the sale proceeds will go to researchers at the Francis Crick Institute in London, Crick's family said.
"This marks the 60th anniversary of the historic discovery of the structure of DNA and 50 years have passed since Francis Crick was awarded the Nobel Prize," granddaughter Kindra Crick said.
"Our hope is that, by having it available for display, it can be an inspiration to the next generation of scientists."