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Chromatin circles in amphibian previtellogenic oocytes

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Summary

Previtellogenic oocytes ofOdontophrynus americanus display hundreds of chromatin circles. Electron microscopy of spread preparations of isolated nuclei shows that the circles originate from the chromatin. The circles change their morphology and form new copies. The length of the DNA packed in the nucleosomal circles is about 2.5–3.5 μm or multiples of this value. Assuming that histones need not be removed from chromatin before DNA replication3 we suggest that the circles might belong to the process of rDNA amplification.

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Authors and Affiliations

  1. Serviço de Genética, Instituto Butantan, São Paulo, Brasil

    Maria Luiza Beçak & Kazumi Fukuda Pizzocaro

Authors
  1. Maria Luiza Beçak
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  2. Kazumi Fukuda Pizzocaro
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Additional information

This work was supported by grants from the Brazilian CNPq, FAPESP and FEDIB.

We thank Dr A. Brunner Jr for the use of the electron microscope and Dr N. Leon for his valuable help.

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Beçak, M.L., Pizzocaro, K.F. Chromatin circles in amphibian previtellogenic oocytes. Experientia 36, 164–166 (1980). https://doi.org/10.1007/BF01953709

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