[Genetically based diseases]

Genetics is one of the greatest scientific advances of the XX century, which begins with the rediscovery of Mendel's laws and culminates in the elaboration of the first "draft" of the complete sequence of the human genome. Genetics employs different research strategies, such as the study of twins and adoption, investigating the influence of genetic and environmental factors, and strategies for identifying specific genes (molecular genetics). Besides the significant degree of disability they generate, the social impact of hereditary diseases is enormous, due to their potentially recurrent character in the same family and the high socio-health cost deriving from the enormous care burden they require. The diagnosis of hereditary diseases presents very significant differentiating characteristics since the result of a genetic diagnosis has effects not only on the patient but also on related individuals. Thus the unit of study in genetic diagnosis is the family and the whole process of diagnosis involves family research. It is also useful to bear in mind that the protocols of diagnosis are developed in parallel with the basic research and in general are hardly standardised. The results obtained in genetic studies and the type of information provided to the patient and his family must be qualified within the process of "genetic counselling".