The Nobel Prize gold medal awarded to the US scientist James Watson for discovering the structure of DNA has sold at auction for $4.8m (£3m).
The 1962 prize was awarded to Watson, Maurice Wilkins and Francis Crick, with each receiving a gold medal.
The medal is the first Nobel Prize to be put on sale by a living recipient.
Watson recently said he was selling the medal because he had been ostracised by the scientific community after remarks he made about race in a 2007 interview.
The discovery of the structure of DNA - which encodes the instruction booklet for building a living organism - was made by Watson and Crick, using experimental data that had been gathered by Maurice Wilkins, Raymond Gosling and Rosalind Franklin.
Mr Watson, 86, said he planned to donate part of the proceeds to charities and to support scientific research.
Christie's auction house had said the gold medal could fetch between $2.5m (£1.6m) and $3.5m (£2.2m).
In an interview with the Financial Times recently, Mr Watson said he had been made to feel like an "unperson" since a Sunday Times interview seven years ago in which he linked race to intelligence.
Francis Crick's Nobel medal sold for $2.2m last year. He died in 2004.