We describe 2 families in which acrocentric short arm material moved from one chromosome to another. In case 1, a meiotic event resulted in movement of an unusually large paternal 21p to chromosome 13 in the fetus. In case 2, a mitotic event resulted in fetal mosaicism. The short arm material from a paternal chromosome 15 moved to chromosome 14 in some of the fetal cells. Movement of acrocentric short arm material resulted from breakage and exchange in centromeric areas of repetitive DNA. We suggest the mechanism may be similar to that of previously reported "jumping" translocations. Failure to recognize movement of the short arms of acrocentric chromosomes can result in erroneous interpretation of prenatal cytogenetic results and of other cytogenetic assays dependent on acrocentric short arm polymorphisms.

In a human lymphoblastoid cell line (Z83) in which rDNA genes on chromosome 22 are amplified but transcribed at a low level, immunocytological studies with antibodies to 5 methylcytidine provided evidence for hypermethylation of the rDNA. The extent of methylation of the 5' flanking sequences of the ribosomal DNA was examined by comparing the size of restriction fragments obtained by digestion of genomic DNA with EcoRI and HpaII or EcoRI and MspI. Southern blots indicated hypermethylation of the 5' flanking sequences of many copies of rRNA genes in these cells, but not in a control lymphoblastoid cell line without rDNA amplification. Results obtained with a somatic hybrid human-hamster cell line, in which the rRNA genes on the single human chromosome 22 are inactive, showed that only a small fraction of the CCGG sites in the 5' flanking sequences of the transcriptionally silent rRNA genes in this hybrid were methylated. Since inactive rRNA genes can show such a minimal level of methylation, it is likely that the extreme hypermethylation of the amplified rRNA genes in Z83 occurred in association with their inactivation rather than following it.

Prenatal DiagnosisVolume 12, Issue 5 p. 439-441 Article Annex 5: List of all cytogenetic abnormalities detected D. J. Tomkins, D. J. Tomkins McMaster University, Hamilton, Ontario, CanadaSearch for more papers by this authorM. J. J. Vekemans, M. J. J. Vekemans McGill University, Montreal, Quebec, CanadaSearch for more papers by this authorI. E. Teshima, I. E. Teshima University of Toronto, Ontario, CanadaSearch for more papers by this authorD. M. Cox, D. M. Cox University of Calgary, Alberta, CanadaSearch for more papers by this authorL. Dallaire, L. Dallaire University of Montreal, Quebec, CanadaSearch for more papers by this authorR. Gagne, R. Gagne Laval University, Quebec City, Quebec, CanadaSearch for more papers by this authorD. K. Kalousek, D. K. Kalousek University of British Columbia, Vancouver, CanadaSearch for more papers by this authorJ. C. C. Lin, J. C. C. Lin University of Alberta, Edmonton, CanadaSearch for more papers by this authorV. D. Markovic, V. D. Markovic Surrey Place Centre, Toronto, Ontario, CanadaSearch for more papers by this authorM. Ray, M. Ray University of Manitoba, Winnipeg, CanadaSearch for more papers by this authorF. R. Sergovich, F. R. Sergovich University of Western Ontario, London, Ontario, CanadaSearch for more papers by this authorI. A. Uchida, I. A. Uchida McMaster University, Hamilton, Ontario, CanadaSearch for more papers by this authorH. Wang, H. Wang University of Ottawa, Ontario, CanadaSearch for more papers by this author D. J. Tomkins, D. J. Tomkins McMaster University, Hamilton, Ontario, CanadaSearch for more papers by this authorM. J. J. Vekemans, M. J. J. Vekemans McGill University, Montreal, Quebec, CanadaSearch for more papers by this authorI. E. Teshima, I. E. Teshima University of Toronto, Ontario, CanadaSearch for more papers by this authorD. M. Cox, D. M. Cox University of Calgary, Alberta, CanadaSearch for more papers by this authorL. Dallaire, L. Dallaire University of Montreal, Quebec, CanadaSearch for more papers by this authorR. Gagne, R. Gagne Laval University, Quebec City, Quebec, CanadaSearch for more papers by this authorD. K. Kalousek, D. K. Kalousek University of British Columbia, Vancouver, CanadaSearch for more papers by this authorJ. C. C. Lin, J. C. C. Lin University of Alberta, Edmonton, CanadaSearch for more papers by this authorV. D. Markovic, V. D. Markovic Surrey Place Centre, Toronto, Ontario, CanadaSearch for more papers by this authorM. Ray, M. Ray University of Manitoba, Winnipeg, CanadaSearch for more papers by this authorF. R. Sergovich, F. R. Sergovich University of Western Ontario, London, Ontario, CanadaSearch for more papers by this authorI. A. Uchida, I. A. Uchida McMaster University, Hamilton, Ontario, CanadaSearch for more papers by this authorH. Wang, H. Wang University of Ottawa, Ontario, CanadaSearch for more papers by this author First published: May 1992 https://doi.org/10.1002/pd.1970120513Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume12, Issue5Special Issue: Collaborative Studies on Chorion Villus Sampling in North AmericaMay 1992Pages 439-441 RelatedInformation