[A second example of telomeric fusion 2 X chromosomes].

A translocation which originated by telomeric "fusion" of X short arms, t(X;X), was found in a woman with primary amenorrhea and a phenotype corresponding partially to Turner's syndrome. Staining with acridine orange after BrdU incorporation showed the distal segments of both Xp's to be much more modified by the treatment than equivalent segments of normal late replicating X's. This could mean important inactivation of segments usually active even in late replicating X's. This functional monosomy for X would have a clinical effect similar to a true monosomy.