Expression of the fragile site Xq27 in fibroblasts. I. Detection of fra(X)(q27) in fibroblast clones from males with X-linked mental retardation.

Twelve fibroblast clones from two males with X-linked mental retardation expressed the fragile site Xq27 in 3%-38% of metaphases analyzed. The number of in vitro doublings during the cloning procedure had no evident influence on the induction of fragile X expression. The variability of fragile X expression seems to depend on cell properties acquired during culture rather than on properties originally inherent in the cells.