A massive research project has effectively scrapped the concept of 'junk' DNA and paved the way for a medical revolution.
The findings, reported in some 30 research papers, show that around 80pc of the genetic code is actively involved in keeping life going.
A team of more than 400 scientists from 32 laboratories around the world identified four million 'switches' that determine whether genes are turned on or off.
In future, scientists hope the findings will lead to a deeper understanding of numerous diseases and help them devise more effective diagnostic tools and treatments.
Until recently, large amounts of the human genetic code -- or genome -- were dismissed as 'junk' -- DNA sequences that had no function.
Experts only began to realise that junk DNA might have a useful regulatory role in the 1990s. But even 10 years ago, when the Human Genome Project mapped the first definitive blueprint of the 'book of life', much of the genome was thought to be junk.
Now scientists know that almost every fragment of DNA has a purpose.
Speaking at the Science Museum in central London yesterday, Dr Ewan Birney, chief analysis co-ordinator on the Encyclopedia of DNA Elements project, known as Encode, said: "We're going to find out ways of helping us understand disease, avoid disease, prevent disease and perhaps cure disease in different ways from this, but I'm not going to be able to put my finger on this disease or that disease right now.
"It's clinical researchers and doctors who are going to be the people who I think will benefit from this. I'm a kind of servant to that community of researchers."
The scientist said the new information should not only be appreciated by scientists and doctors, but by everyone who wants to understand how humans work.