Inherited defects in a gene on a chromosome are strongly implicated in predisposing some children to dyslexia, the scientists report today in the journal Science.
They believe the discovery could lead to the identification of potentially dyslexic children before they go to school and help correct reading disabilities early in life.
Bruce Pennington, Professor of Psychology at the University of Denver, United States, said: 'What is inherited is a gene that affects some aspect of the way the brain develops. That in turn affects some aspect of language development so that it makes reading difficult.'
The scientists from four US research centres, led by Lon Cardon of Stanford University, interviewed more than 450 members of families with a history of reading disabilities, including 100 non-identical twins where at least one in each pair was dyslexic.
By analysing the DNA of the family members, the researchers found that a region of chromosome 6 - one of the 23 pairs in humans - was significantly implicated with reading disability.
Professor Pennington said the gene must be reasonably common and could account for a substantial number of the 5 to 10 per cent of children with reading disabilites.