Genes for cognitive function: Developments on the X

Developments in human genome research enabled the first steps toward a mole cular understanding of cognitive function. That there are numerous genes on the X chromosome affecting intelligence at the lower end of the cognitive range is no longer in doubt. Naturally occurring mutations have so far led to the identification of seven genes accounting for a small proportion of f amilial nonspecific X-linked mental retardation. These new data indicate th at normal expression of many more X-linked and autosomal genes contribute t o cognitive function. The emerging knowledge implicating genes in intracell ular signaling pathways provides the insight to identify as candidates othe r X-linked and autosomal genes regulating the normal development of cogniti ve function. Recent advances in unravelling the underlying molecular comple xity have been spectacular but represent only the beginning, and new techno logies will need to be introduced to complete the picture.