A possible active segment on the inactive human X chromosome |
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Authors: | Eeva Therman Gloria E Sarto C Distèche Carter Denniston |
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Institution: | (1) Department of Medical Genetics, University of Wisconsin, 53706 Madison, Wisconsin, USA;(2) Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois, USA;(3) Laboratoire de Cytogénétique, Université de Liège, Belgium |
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Abstract: | An idic(Xp-) in which the two X chromosomes are attached short arm to short arm, and which thus has two b regions (the Q-dark segment next to the centromere on Xp) between the inactivation centers, assumed to be situated on the Q-dark region next to the centromere on Xq, showed 63.8% bipartite Barr bodies as compared with 22.2% formed by idic(Xq-). In addition, the mean distance of the two parts of the Barr bodies in the fibroblasts of a patient with idic(Xp-) is significantly greater than in the cases with one or no b region. Contrary to the other patients with abnormal X chromosomes, the buccal cells of a woman idic(Xp-) showed a number of bipartite Barr bodies. — To explain these observations we have put forward the hypothesis that the b region on the Xp always remains active and thus, when the rest of the chromosome forms a Barr body, this segment is extended, allowing the two parts of the X chromatin to get farther apart and at the same time increasing the percentage of bipartite bodies. |
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