caa a22 4500 467984891 CHVBK 20180323112529.0 cr unu---uuuuu 170328e19901001xx s 000 0 eng 10.1007/BF00193594 doi (NATIONALLICENCE)springer-10.1007/BF00193594 Fragile×expression and×inactivation [Elektronische Daten] I. The expression of the fragile site at Xq27.3 is not suppressed on inactive×chromosomes separated from the active homologue [Doris Wöhrle, Jean-Pierre Fryns, Peter Steinbach] Summary: The inactive fragile×chromosomes of a 47,fra(X),fra(X),Y male with a typical fragile×phenotype were successfully separated from the active homologues by means of somatic cell hybridization. It was shown by FUdR-induction and caffein-posttreatment that the separated inactive×chromosomes expressed their fragile sites and that the presence of an active mutated \sxchromosome was not a prerequisite for fragile X expression. The fragility seems to be an intrinsic property of the individual fragile site. This result is in favour of the classical concept that the fragile site at Xq27.3 has a primary pathogenetic function in this syndrome, although the fragility itself could represent a secondary phenomenon related to an unknown alteration of the DNA in this chromosome region. It is also concluded that inactivation of the fragile\sxchromosome in females is not responsible for either false negative fragile\sxfindings or the observation of fragile\sxnegative colonies isolated from fragile\sxpositive fibroblasts in heterozygotes. Springer-Verlag, 1990 Wöhrle Doris Abteilung Klinische Genetik der Universität, Frauenstrasse 29, W-7900, Ulm, Germany aut Fryns Jean-Pierre Division of Human Genetics, University Hospital Gasthuisberg, B-3000, Leuven, Belgium aut Steinbach Peter Abteilung Klinische Genetik der Universität, Frauenstrasse 29, W-7900, Ulm, Germany aut Human Genetics Springer-Verlag 85/6(1990-10-01), 659-665 0340-6717 85:6<659 1990 85 439 https://doi.org/10.1007/BF00193594 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00193594 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Wöhrle Doris Abteilung Klinische Genetik der Universität, Frauenstrasse 29, W-7900, Ulm, Germany aut NATIONALLICENCE 700 1- Fryns Jean-Pierre Division of Human Genetics, University Hospital Gasthuisberg, B-3000, Leuven, Belgium aut NATIONALLICENCE 700 1- Steinbach Peter Abteilung Klinische Genetik der Universität, Frauenstrasse 29, W-7900, Ulm, Germany aut NATIONALLICENCE 773 0- Human Genetics Springer-Verlag 85/6(1990-10-01), 659-665 0340-6717 85:6<659 1990 85 439 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer