The three winners, Carol Greider, Jack Szostak, and Elizabeth Blackburn, were awarded the prize “for the discovery of how chromosomes are protected by telomeres and the enzyme telomerase”.

“I’m extremely wound up. I’m quite nervous and shaking inside, but I feel a great honour – you never expect to have a conversation like this,” Greider told the TT news agency be telephone about an hour after the Nobel Committee’s announcement.

Greider, who teaches at Johns Hopkins University in Baltimore and whose name had been mentioned as a possible winner in the run-up to the announcement, added it had been suggested to her that she could receive a call from the Swedish capital early Monday.

She was preparing her children’s breakfast when Swedish radio called to interview her.

“I was awake, I wake up early anyway, I was doing the laundry when the phone call came” she told Sveriges Radio.

Groundbreaking research by Greider, Szostak, and Blackburn helped solve one of biology’s greatest mysteries: how chromosomes, which contain hereditary material, can be copied during cell division and how they are protected from being broken down.

They showed that the explanation for the key molecular switch in cellular ageing lies in the ends of chromosomes, telomeres, and in an enzyme, telomerase, which creates them.

Back in the 1980s, Blackburn and Szostak discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation.

Meanwhile, Greider and Blackburn identified telomerase, the enzyme that makes telomere DNA.

Together the discoveries help explain how the ends of the chromosomes are protected by the telomeres and that they are built by telomerase.

The research has significance for developing new therapies to treat cancer and hereditary diseases.

“We’d been hunting for this enzyme and when the first clear signs of it appeared … I thought ‘this is very interesting, this is a very important result,’ and you don’t often feel that about a result,” Blackburn said.

Szostak was overjoyed when speaking to SR from his home in Boston.

He explained that the Nobel committee’s call had woken him up, even though he had considered the “not very likely” possibility an early morning call could come from Sweden.

“I said (to my wife) it’ll probably come at around 5:30 am, but it came much earlier so I was still sound asleep,” he said, a chuckle in his voice.