Molecular markers of fragile X: recent research developments

Linkage studies are a powerful method for studying the inheritance of a genetic locus such as the fra(X) mutation where variable penetrance is present. These studies are dependent on the informativeness and availability of flanking DNA probes. Until 1989, no probes had been identified which detected loci closer than about 5 recom- bination units away from the fra(X) mutation. However, now at least four loci are known and the methods that have been employed to identify these probes will certainly lead to the identification of many more new probes that are in the immediate neighborhood of the fra(X) mutation. Progress in the characterization of such closely flanking probes should rapidly lead to a molecular understanding of the nature of the fra(X) mutation.