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Published June 15, 1973 | public
Journal Article

General interspersion of repetitive with non-repetitive sequence elements in the DNA of Xenopus

Abstract

The arrangement of repetitive and non-repetitive sequences was studied in the DNA of Xenopus. Labeled DNA sheared to various fragment lengths was reassociated to C_ot 50 (60 °C, 0.18 m-Na^+) with excess 450 nucleotide fragments of unlabeled DNA, and binding of the labeled DNA to hydroxyapatite was measured. Repetitive sequences monitored in this way are present on about 45% of the 450 nucleotide fragments. As DNA fragment length is increased, larger fractions of the DNA are found to contain repetitive elements. Up to 80% of the DNA binds at an average fragment length of 3700 nueleotides. Analysis of the data shows that a little more than 50% of the genome consists of closely interspersed repetitive and non-repetitive sequences. The average length of the repetitive sequence elements is 300±100 nueleotides, while the non-repetitive sequences separating adjacent repetitive sequence elements average 800±200 nueleotides. The remainder of the DNA is mainly non-repetitive, though most of it contains rare interspersed repetitive elements spaced at a minimum of 4000 nueleotides apart. It is concluded that a high degree of order exists in the arrangement of DNA sequences in the Xenopus genome.

Additional Information

© 1973 Elsevier. (Received 23 October 1972, and in revised form 22 January 1973) This research was supported by the National Institute of Child Health and Development grant no. HD-05753, National Science Foundation grants nos GB-33441X and GB-32281, and American Cancer Society grant E-334-E. We acknowledge the expert technical assistance of Ms Margaret Chamberlin. We are appreciative of the kind gifts of DNA made to us by Dr Donald R. Brown of the Carnegie Institution of Washington, Baltimore, Md., and Dr Stephen Harris of the California Institute of Technology. We would particularly like to thank Professors James Bonner and Norman Davidson of this Institute for critical reviews and discussions of the manuscript. One of us (R. J.B.) is a staff member of the Carnegie Institute of Washington, and a Research Associate of the California Institute of Technology.

Additional details

Created:
August 19, 2023
Modified:
October 19, 2023