Localization and Identification of Genes
Affecting Language and Learning
Shelley D. Smith
University of Nebraska Medical Center
Serious language and learning problems occur in as much as 10% of school children, but the underlying causes are unknown, making it difficult to develop specific diagnostic criteria and tailor appropriate remediation. Family and twin studies indicate that genetic factors influence the most common disorders—specific language impairment (SLI), dyslexia, and attention deficit/hyperactivity disorder (ADHD)—but environmental factors are also important. These nature and nurture influences may be present to different degrees in different individuals and their families, and they may even interact. Furthermore, the genetic influences may differ because there is evidence for multiple genes affecting these conditions. Identification of either the environmental or genetic mechanisms would help sort this heterogeneous population into subgroups with similar etiologies so that the mechanisms can be investigated and understood. The complexity of these traits has made the identification of specific genes challenging, but recent developments in molecular and statistical technologies are promising, giving hope that genes for these conditions will finally be identified.
Identification of mutations in genes affecting complex cognitive disorders could have practical advantages, although these should not be overstated. Preclinical diagnosis would be possible, allowing the identification of at-risk children and the development of effective means of remediation before the children experience frustration and failure. However, the actual application of such screening depends on the proportion