Different inducibility and possible significance of several concomitant "fragile sites" in two brothers.

Concomitance of four fragile sites (at 16p13, 16q22, 16q23, Yq12) in the lymphocyte cultures of two brothers is reported. The expression of each of these fragile sites was enhanced (or induced) by different culture conditions. Some of the inducing conditions are already known and others are reported here for the first time. The meaning of the fragile sites is discussed and a possible viral etiology suggested. Concomitance of some of them may be a potential causal factor for deletions, translocations, or inversions.