The discipline of genetic epidemiology pertains to the vertical transmission of the susceptibility (predisposition) to a complex disease in a structured population. This statement meets halfway 1 the broad definitiongiven by N. E. Morton and S. c. Chung in 1978 2 and the concise one given by M. -C. King et al. in 1984. 1t pinpoints the fundamental genetic hypothesis, namely, the existence of an inherited condition that predisposes an individual to a specific disease, and the corresponding subject ofinvestigation, the family. Thus, the genetic epidemiological situation consists of three basic elements: (l) the genealogical structure, (2) the mode of inherit­ ance (i. e. , the "genetic model") for the trait of interest, and (3) the observable phenotypes of susceptibility. It is clear that genetic epidemiology is a research field posi­ tioned at the intersection of molecular genetics, population gen­ etics, and clinical genetics. Perhaps the genealogical tree should be its central element: it evidences something forgotten in mole­ cular genetics, namely the relationships, and associations with probabilistic and statistical concepts from population genetics. It offers a structure and a "history" for those clinicians studying familial diseases who are searching for genetic determinants of susceptibility. The genetic epidemiologist begins his analysis with a point on this genealogical tree, namely the proband, and attempts to carry out (nonrandom) "ascertainment sampling" by using a strategy that depends on the form and dimension (extended pedigrees versus nuclear families) of the tree.

The discipline of genetic epidemiology pertains to the vertical transmission of the susceptibility (predisposition) to a complex disease in a structured population. This statement meets halfway 1 the broad definitiongiven by N. E. Morton and S. c. Chung in 1978 2 and the concise one given by M. -C. King et al. in 1984. 1t pinpoints the fundamental genetic hypothesis, namely, the existence of an inherited condition that predisposes an individual to a specific disease, and the corresponding subject ofinvestigation, the family. Thus, the genetic epidemiological situation consists of three basic elements: (l) the genealogical structure, (2) the mode of inherit­ ance (i. e. , the "genetic model") for the trait of interest, and (3) the observable phenotypes of susceptibility. It is clear that genetic epidemiology is a research field posi­ tioned at the intersection of molecular genetics, population gen­ etics, and clinical genetics. Perhaps the genealogical tree should be its central element: it evidences something forgotten in mole­ cular genetics, namely the relationships, and associations with probabilistic and statistical concepts from population genetics. It offers a structure and a "history" for those clinicians studying familial diseases who are searching for genetic determinants of susceptibility. The genetic epidemiologist begins his analysis with a point on this genealogical tree, namely the proband, and attempts to carry out (nonrandom) "ascertainment sampling" by using a strategy that depends on the form and dimension (extended pedigrees versus nuclear families) of the tree.

The discipline of genetic epidemiology pertains to the vertical transmission of the susceptibility (predisposition) to a complex disease in a structured population. This statement meets halfway 1 the broad definitiongiven by N. E. Morton and S. c. Chung in 1978 2 and the concise one given by M. -C. King et al. in 1984. 1t pinpoints the fundamental genetic hypothesis, namely, the existence of an inherited condition that predisposes an individual to a specific disease, and the corresponding subject ofinvestigation, the family. Thus, the genetic epidemiological situation consists of three basic elements: (l) the genealogical structure, (2) the mode of inherit­ ance (i. e. , the "genetic model") for the trait of interest, and (3) the observable phenotypes of susceptibility. It is clear that genetic epidemiology is a research field posi­ tioned at the intersection of molecular genetics, population gen­ etics, and clinical genetics. Perhaps the genealogical tree should be its central element: it evidences something forgotten in mole­ cular genetics, namely the relationships, and associations with probabilistic and statistical concepts from population genetics. It offers a structure and a "history" for those clinicians studying familial diseases who are searching for genetic determinants of susceptibility. The genetic epidemiologist begins his analysis with a point on this genealogical tree, namely the proband, and attempts to carry out (nonrandom) "ascertainment sampling" by using a strategy that depends on the form and dimension (extended pedigrees versus nuclear families) of the tree.