Search for genes linked to intelligence

Australian scientists have identified two regions of human genetic material which they believe harbour genes that influence a person's IQ (intelligence quotient). The team, based at the Queensland Institute of Medical Research, say that identifying the genes that affect intelligence could help research into disorders such as dyslexia, autism and attention deficit hyperactivity disorder. The researchers, who published their findings in the American Journal of Human Genetics, say that two such genes are located on chromosomes two and six.

Previous studies have estimated that around 40-80 per cent of the variation in people's intelligence is caused by genes, with the remaining variation caused by non-genetic factors such as upbringing and diet. It is thought that hundreds of different genes influence a person's IQ.

In the latest study, the researchers studied 634 pairs of siblings (including non-identical twins) from Australia and the Netherlands. They found that genetic markers in a region of chromosome two appeared to be linked to a type of intelligence called performance IQ. Traditional IQ tests aim to assess ability in several different areas, one of which is performance intelligence. They also found that a region of chromosome six is linked to 'full-scale' and verbal IQ. This area overlaps slightly with a region implicated in reading disability and dyslexia, suggesting that a common gene is involved in these traits.

Team leader Nick Martin stressed that 'this is a good start but the next, more difficult stage is to find the specific genes in these chromosomal regions which are responsible for variation in intelligence'. He says that the research could help develop new treatments for conditions such as autism, which cause intellectual impairment. He said that such work would have 'great social benefit', but there was a risk, as with any new technology, that it could be misused to discriminate against people.