[Cytogenetic studies in fragile X syndrome].

The main purpose of this work has been to find a method which would enable the diagnosis of FXS at the cytogenetic level. The studies are based on the analysis of chromosomes from 24 cultures on RPMI-1640 base with an addition of 5-fluoro-2'-deoxyuridine (FUdR) as inhibitor of thymidylate synthetase. The results indicate, that the cultures with the addition of FUdR could considerably improve the expression of fragile X chromosome. It is of great importance, particularly un the cases in which the presence of this marker is very low. It was possibly to specify the significant percentage and the exact position of breaks, gaps and fragile sites, mostly present in autosomes. It could mean, that such factors may play a significant role, apart of X chromosome, in the pathogenesis of FXS. The results of work prove, that this kind of method could be used as a screening for cases with fragile X syndrome.