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Spontaneous fragility of an abnormally wide secondary constriction region in a human chromosome No. 9

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Summary

In an infant with clinically and cytologically typical Down's syndrome a chromosome No. 9 was found exhibiting an exceptionally large paracentric constriction which proved to be spontaneously fragile. In cells in which this chromosome was broken the centric portion was present whereas the acentric fragment was absent. A No. 9 chromosome with identical morphology was found in the karyotype of the father but no fragility was evident. Autoradiography revealed pronounced late replication in the constriction region, suggesting a duplication or insertion of heterochromatic material. Clinically there was no evidence for any phenotypic expression of this cytological anomaly.

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Authors and Affiliations

  1. Department of Pediatrics, University of Zurich, (Switzerland)

    W. Schmid & D. Vischer

  2. Genetisches Labor, Universitäts-Kinderklinik, Steinwiesstraße 75, CH-8032, Zürich

    W. Schmid

Authors
  1. W. Schmid
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  2. D. Vischer
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Supported in part by the Swiss National Foundation

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Schmid, W., Vischer, D. Spontaneous fragility of an abnormally wide secondary constriction region in a human chromosome No. 9. Hum Genet 7, 22–27 (1969). https://doi.org/10.1007/BF00278689

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  • DOI: https://doi.org/10.1007/BF00278689

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