Briton shares Nobel Prize for 'junk' discovery: Scientists awarded accolade for DNA research. Tom Wilkie reports

TWO RESEARCHERS, one a Briton working in the United States, have received the Nobel Prize for discovering the outstanding mystery of modern genetics: that most DNA is 'junk'.

The Karolinska Institutet has awarded the 1993 prize for Medicine or Physiology jointly to Richard Roberts and Phillip Sharp, an American. They gained the award, worth a total of 6.7 million Swedish kronor (pounds 553,700), for their discovery in 1977 of 'split genes'.

Among the applications that have stemmed from the discovery is the 'genetic fingerprinting' developed by Professor Alec Jeffreys at the University of Leicester. The discovery has illuminated the mechanisms underlying such genetic diseases as Duch enne Muscular Dystrophy, and has also thrown light on how evolution works at a molecular level.

Professor Sharp, 49, head of the department of biology at the Massachusetts Institute of Technology, said he planned to celebrate with his wife and three daughters.

Dr Roberts, 50, was born in Derby, graduated from Sheffield University and later worked as a research associate at Harvard University. In 1972, he started work at Cold Spring Harbor Laboratory where he carried out the prize-winning research. Since 1992 he has been research director at New England Biolabs in Massachusetts.

Genes are recipes written out along the double-helix strand of DNA: every gene contains instructions for living cells to make a protein - the biochemicals essential for life. The researchers discovered that most of the text in these genetic recipes is gibberish - there are long stretches of DNA within a gene which do not contain the recipe for any protein.

Researchers have since established that about 90 per cent of a human being's DNA is meaningless 'junk'. Its presence, between genes as well as inside them, means that there is no direct correlation between the complexity of a creature and the length of its DNA. The DNA of humans is about 1,000 times as long as that of simpler organisms such as bacteria, but lilies and salamanders have 20 to 30 times as much DNA as humans.

Such junk DNA has also been implicated in human disease. The gene implicated in Duchenne Muscular Dystrophy is one of the longest known: it contains about 2 million units, known as base-pairs. But the recipe for the protein dystrophin is only about 14,000 base-pairs long - less than 0.7 per cent. The rest of the gene consists of gibberish.

The stretches of nonsense can make the gene unstable and, in children affected by the disease, cause the cell to manufacture a defective form of the protein. About one 1 in 3,500 boys is born with the disease.

Dr Roberts and Professor Sharp made their initial discovery by studying the genetic material of a very simple organism: a virus that causes the common cold.

(Photograph omitted)