Approaches to the study of the genetic basis of common complex diseases and their clinical applications are considered. Monogenic Mendelian inheritance in such conditions is infrequent but its elucidation may help to detect pathogenic mechanisms in the more common variety of complex diseases. Involvement by multiple genes in complex diseases usually occurs but the isolation and identification of specific genes so far has been exceptional. The role of common polymorphisms as indicators of disease risk in various studies is discussed.
Genetic Diseases, Inborn ; genetics ; Genetic Predisposition to Disease ; Genetic Techniques ; Humans ; Inheritance Patterns ; Linkage Disequilibrium ; Models, Genetic ; Polymorphism, Genetic ; Risk Factors

Pharmacogenetics and pharmacogenomics deal with the role of genetic factors in drug effectiveness and adverse drug reactions. The promise of a personalized medicine is beginning to be explored but requires much more clinical and translational research. Specific DNA abnormalities in some cancers already have led to effective targeted treatments. Racially determined frequency differences in pharmacogenetic traits may affect choice of treatment requiring specific testing rather than basing treatments according to racial designation. The role of genes in variable responses to foreign chemicals (xenobiotics) has been termed ecogenetics or toxicogenetics raising problems in public health and occupational medicine. Nutrigenetics refers to genetic variation in response to nutrients and may affect nutritional requirements and predisposition to chronic disease.
DNA ; analysis ; Drug-Related Side Effects and Adverse Reactions ; Ecology ; Genetic Variation ; Genome, Human ; Genotype ; Humans ; Nutritional Physiological Phenomena ; Pharmaceutical Preparations ; Pharmacogenetics ; methods ; Phenotype ; Xenobiotics