[The genetic approaches of the disorders of the child]

Genetics, which encompasses cytogenetic, molecular genetics, genetic of populations, pharmacogenetics and gene therapy, become as numerous and almost independent applications (fields). Deriving from the original questions on the origin and mechanisms of diseases, these represent essential tools to better understand physiopathogenesis. Cytogenetics (Chromosomes study, aberrations and their impact on the apparition of diseases) and genomics (the understand of the structure, organisation and DNA expression) are dedicated to clinical genetics as diagnostic and basic science improvements. The identification of new mechanisms of diseases were responsible for the creation of new tools which allow in turn to precise the intimate and underlying processes of diseases or syndromes. Due to the explosion of findings and research programs on fetal, embryologic and pediatric fields, laboratory and reference centers were build. Any child identified as carrier and/or affected from a pathogenic mutation became the primary step for the development of fetal, prenatal and preimplantatory medicines. Ethics came into play since responsibilities for 'do not harm', 'eugenism' temptations and 'individual life' with respect to medical laws should be guaranteed. These are part of the geneticist tasks and the reasons for professionalisation as for teaching genetics as part of medical traineeships that Paediatrics, among others, represents. The present review will systematically describe the principles of these different genetic fields.