Fragile (X) expression, age and the degree of intellectual handicap in the male.

Abstract

The proportion of cells expressing the fra(X) was compared to the guardian's opinion of who was the "brighter" in 31 sibships of 2 or more affected males. Six fra(X) positive males in the normal workforce were compared in a similar way to other affected relatives. A correlation was found between lower values of expression and "brightness" by the Wilcoxson signed rank test (less than 0.01, 2-tail). A decline in fra(X) expression occurs with age. Some apparently normal non-expressing transmitting males may be accounted for by these findings.