Translocation of the nucleolus organizer region to the human X chromosome.

We report the unique finding of a satellited X chromosome in a woman with Turner syndrome and a mosaic karyotype 45,X/46,X,mar(X)(sat,QFQ55),var(21)(sat,QFQ55). In PHA-stimulated lymphocytes and in lymphoblast culture, the satellited X chromosome was consistently late replicating. The translocated nucleolus organizer region (NOR) genes in the stalk of the satellite, however, remained transcriptionally active, and an unusual, late-replicating band was seen at the distal end of Xp. Analysis of fibroblast clones containing the satellited X chromosome suggests that the mar(X) is relatively stable.