How do cells know when to divide so that an organism can function and develop normally?

The answer lies in cyclins - proteins that act as the human body's internal clock so that cells know when to grow and multiply.

Dr Hunt, 73, was awarded the Nobel Prize in physiology or medicine in 2001 for his discovery of cyclins, which the biochemist named after his hobby of riding a bike.

In 1982, Dr Hunt, who is British, joinedthe Marine Biological Laboratory at Woods Hole, Massachusetts to teach summer courses and to study protein synthesis in sea urchins and fertilised clam eggs.

It was during this period that the first results of his studies began to indicate the presence and function of cyclins.

He found out that cyclins would disappear around the 10-minute mark before cell division, although he could not understand why.

It was only in 1986 that his team managed to understand the mechanism behind how cyclins controlled the cell cycle.

His team did so by cloning the gene responsible for cyclin. Cyclins control cell division. When they are destroyed, the cell goes into the next phase of the cell cycle.

Today, cyclins are featured in high school biology textbooks across the world.

• Source: National Research Foundation