FRAXE AND MENTAL-RETARDATION

Mental impairment and instability of the CCG repeat at FRAXE is descri bed in six kindreds. Cosegregation of FRAXA and FRAXE was found within one of these kindreds. Cytogenetic expression of FRAXE was shown to s kip a generation when associated with a reduction in size of the CCG e xpansion when transmitted through a male; however, in general, transmi ssion occurred through females and copy number increased from one gene ration to the next. In these respects the behaviour of FRAXE parallele d that of FRAXA. A relationship between FRAXE and non-specific mental impairment is strongly suggested by the occurrence in these families o f more mentally impaired male and female carriers, after removal of in dex cases, than could reasonably be expected by chance.