Stockholm: US geneticists Jeffrey C Hall, Michael Rosbash and Michael W Young were awarded the Nobel Medicine Prize today for shedding light on the internal biological clock that governs the wake-sleep cycles of most living things.   

"Their discoveries explain how plants, animals and humans adapt their biological rhythm so that it is synchronised with the Earth's revolutions," the Nobel Assembly announced. Life on Earth is adapted to the rotation of our planet. 

For many years, scientists have known that living organisms, including humans, have an internal clock that help them anticipate and adapt to the rhythm of the day. Hall, 72, Rosbash, 73, and Young, 68, "were able to peek inside our biological clock and elucidate its inner workings," said the Nobel Assembly.   

The clock influences such biological functions as hormone levels, sleep, body temperature and metabolism. It is what causes jetlag when our internal clock and external environment move out of sync when we change time zones.   

Using the fruit fly as a model organism, this year's laureates isolated a gene that controls the daily biological rhythm."They showed that this gene encodes a protein that accumulates in the cell during the night and is then degraded during the day," the Nobel team said.   

"Subsequently they identified additional protein components of this machinery, exposing the mechanism governing the self-sustaining clockwork inside the cell." The trio will share the prize sum of nine million Swedish kronor (about USD 1.1 million or 937,000 euros).  

Last year, Yoshinori Ohsumi of Japan won the prestigious prize for his work on autophagy a process whereby cells "eat themselves", which when disrupted can cause Parkinson's and diabetes.