Summary
Using loop-specific DNA clones, we established that the T (X:Y)56 (Hackstein and Hennig 1982) chromosome, formerly thought to be deleted for the Yshort arm and the associated ‘nooses’ loops is actually an XYS·YL combination. It carries, adjacent to the translocation junction, the complete and uninterrupted set of the two dysfunctional ‘nooses’ domains. The morphologically altered and functionally defective loops are transcribed at about 50% of the normal rate. Transcripts in one of the two ‘nooses’ domains are preferentially underrepresented and their distribution in the spermatocyte nucleus is distorted, presumably as a consequence of a spreading effect. No alteration in transcript size or in the correct strand selection, and no variegation of transcription on the single spermatocyte level, were observed. In another translocation T(X:Y)97, in which ‘tubular ribbons’ were reported to be inactivated (Hess 1970), complete elimination of DNA sequences is observed. A possible mechanism for the possition effect inactivation of Y loops in X:Y translocations is discussed briefly.
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Communicated by M.M. Green
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Lifschytz, E., Hareven, D. Molecular evidence for partial inactivation of Y loops in T(X:Y)56 males from D. hydei . Molec Gen Genet 199, 46–52 (1985). https://doi.org/10.1007/BF00327507
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DOI: https://doi.org/10.1007/BF00327507