Genetic epidemiology has advanced from its early focus on rare mendelian diseases to the genetic dissection of complex traits. With the advent of the complete genome map of humans and other organisms, more than ever genetic epidemiology has an important role in ascertaining the relative importance of genetic and environment causative factors of complex traits. The main methodology strategies (familial resemblance, segregation analysis, association and linkage analysis and meta-analysis) in the study of complex traits are outlined and its advantages and shortcomings are discussed. The importance of sampling and the use of appropriate phenotypes and genetic markers are stressed and an example on the study of BMI (Body Mass Index), showing the role of a major genetic factor located at chromosome 7 illustrates some of the above strategies. It is suggested that in the future, although recognizing that multiplex families will still be the mainstay of linkage studies, new and efficient types of sampling (unrelated controls, for instance) utilizing pooled DNA samples will be universally employed. The recognition of genetic heterogeneity between studies and its interpretation will be one of the proeminent features in the forthcoming complex traits studies.
Familial resemblance; Segregation analysis; Association and linkage analysis; Meta-analysis; Complex traits