Unraveling the genetic component of multifactorial diseases: Dream or reality

The etiology of many human diseases is complex and very likely involves a c ombination of genetic and environmental risk factors. A popular strategy to detect genetic risk factors is to perform a systematic screening of the ge nome searching for linkage. The power of such an approach depends very much on the unknown characteristics of the genetic factors and the main difficu lty is to establish a good trade-off between false positives and false nega tives. Besides, a precise localisation of the risk factor will generally no t be obtained. The set up of a candidate gene strategy is necessary to go f urther in genetic factor identification. It is likely that for multifactori al diseases the only genetic risk factors that can be detected are those wi th fairly strong effects. Even in that case, it is important to design stra tegies which increase the power of detection and provide for a better evalu ation of the associated risks.