Abstract

Le syndrome de retard mental avec chromosome X fragile est l'une des maladies hereditaires les plus frequentes. Il cause un retard mental modere a severe chez 1 homme sur 1250 et un retard mental plus leger chez 1 femme sur 2500. Suite a l'identification du gene en 1991, il a ete possible de mettre en evidence les mutations responsables de ce syndrome. Il s'agissait des premieres mutations dynamiques identifiees. Malgre cela, plusieurs questions demeurent concernant les mecanismes d'expansion (mitotiques et "meiotiques"), de transmission ainsi que sur la prevalence des porteurs sains dans la population generale. Ce dernier point fait plus particulierement l'objet du present memoire et quelques resultats sur la transmission des mutations X fragiles dans les familles sont egalement presentes en deuxieme partie.

Alternate abstract:

Mental retardation syndrome with fragile X chromosome is one of the most common hereditary diseases. It causes moderate to severe mental retardation in 1 in 1250 men and milder mental retardation in 1 in 2500 women. Following the identification of the gene in 1991, it was possible to highlight the mutations responsible for this syndrome. These were the first dynamic mutations identified. Despite this, several questions remain regarding the mechanisms of expansion (mitotic and "meiotic"), transmission as well as the prevalence of healthy carriers in the general population. This last point is more particularly the subject of this report and some results on the transmission of fragile X mutations in families are also presented in the second part.