An international team of researchers say they have discovered a genetic basis for dyslexia - a condition which results in problems with reading and writing.

In a report in the British Journal of Medical Genetics, they describe how a family with a large number of dyslexic members provided the vital clues to their discovery.

The researchers hope their findings will enable dyslexic children to be diagnosed much earlier, so they can be trained to overcome their condition.

A genetic basis for dyslexia has long been suspected. But this is the first time a particular gene has actually been identified.

Researchers from Norway, Belgium and the United States discovered a Norwegian family with a large proportion of dyslexic members.

They tested more than 30 members of the family to see how well they could read and recognise unfamiliar words.

From this, 11 people were found to be dyslexic.

The scientists then took blood samples from all the family members to analyse their genes. And they discovered one short sequence of genetic material appeared to be causing the family's tendency for dyslexia.

Early diagnosis

The discovery has important implications for being able to recognise the condition early.

At present it is not until a child has learnt to read and write that the problem of dyslexia comes to light.

Now, Dr Toril Fagerheim, who led the research, hopes that some day, children with a family history of dyslexia will receive genetic tests when they start school, to establish whether they're likely to need extra training.

She says that having the gene for dyslexia does not mean a child will necessarily become dyslexic - environmental factors are believed to play a part as well.