ABSTRACT
Traditionally the fi eld of genetics was considered a specialized discipline that focused upon severe but relatively rare disorders caused by mutations in single genes. The aim was to identify the genes involved by exploiting existing information regarding inheritance patterns and disease pathology. For example, the cloning of the gene causing Duchenne Muscular Dystrophy was aided by the characterization of chromosome abnormalities in affected patients, whereas the isolation of the β globin gene, which causes sickle-cell anemia, was facilitated by the purifi cation of the damaged protein from red blood cells. Such research was often
driven by the premise that gene identifi cation would ultimately enable a cure either directly, via the correction of the genetic code or replacement of the damaged protein, or indirectly, through the development of pharmaceuticals that restored chemical balance to the affected pathway. As information regarding single-gene disorders grew and laboratory and computational techniques advanced, the interests of researchers broadened to include more common traits that are believed to be infl uenced by genetic factors. These complex, or polygenic, genetic disorders typically have more unpredictable and less pervasive presentation than classic single-gene disorders but nonetheless affect a large number of individuals and therefore represent a signifi cant burden upon health services. In this chapter, we describe
briefl y the methods used to identify genes that contribute to complex genetic traits and, using SLI and dyslexia as examples, we discuss the diffi culties of interpreting, applying, and integrating the information yielded by such studies. Finally, we use FOXP2 to exemplify the ways in which gene mapping can aid our knowledge and understanding of neurodevelopmental disorders.
