Inactivation pattern of the fragile X in heterozygous carriers

In this report we present new data on BrdU-inactivation studies in lymphocytes of five heterozygotes. The present data confirm our previous findings that the prediction of the mental status of female heterozygote carriers cannot be based on the X-inactivation pattern. The general tendency to carry the fragile site on the active X is confirmed and the results of previous studies and hypotheses are reviewed.