A letter the scientist Francis Crick wrote to his son about his Nobel prize-winning DNA discovery has been sold at a New York City auction for a record-breaking $5.3m (£3.45m).

In the 19 March 1953 handwritten letter to his 12-year-old son Michael, Crick describes his discovery of the structure of DNA as something "beautiful". The note tells his son how he and James Watson found the copying mechanism "by which life comes from life". It includes a simple sketch of DNA's double helix structure, which Crick concedes he can't draw very well.

The seven-page letter, written to his son in boarding school, concludes: "Read this carefully so that you will understand it. When you come home we will show you the model. Lots of love, Daddy."

Crick, who died in 2004 at age 88, was awarded the Nobel prize along with Watson and Maurice Wilkins.

On Thursday the molecular biologist's 1962 Nobel prize medal in physiology or medicine will be offered by Heritage Auctions, which estimates it could fetch over $500,000.

The items are among a dozen artefacts Crick's heirs are selling to benefit scientific research. Half the proceeds from the Christie's sale would benefit the Salk Institute for Biological Studies in La Jolla, where Crick was a professor, the granddaughter said. Twenty percent of the proceeds from the Heritage Auctions sale would go to the new Francis Crick Institute in London, a medical research institute due to open in 2015.

The price was a record for a letter sold at auction, Christie's said, eclipsing an Abraham Lincoln letter that sold in April 2008 for $3.4m including commission.

Other items in the Heritage sale include Crick's endorsed Nobel prize cheque in the amount of 85,739,88 Swedish krona, dated 10 December 962, and a white lab coat complete with stains and wear.