ARTICLE

MINOR COMPONENTS OF THE DNA OF PHYSARUM POLYCEPHALUM

Charles E. Holt ¹ and Elizabeth G. Gurney ¹

¹ From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.

Mrs. Gurney's present address is The Department of Genetics, University of California, Berkeley, California 94720

DNA metabolism in the slime mold Physarum polycephalum was studied by centrifugation in CsCl of lysates of cultures labeled with radioactive thymidine at various times in the cell cycle. During the G₂ (premitotic) phase of the cell cycle, two components of the DNA are labeled. One component is lighter (buoyant density 1.686 g/cc) than the mean of the principal DNA (1.700 g/cc), and one is heavier (approximately 1.706 g/cc). The labeled light DNA was identified chemically by its denaturability, its susceptibility to DNase, and the recovery of its radioactivity in thymine. Cell fractionation studies showed that the heavy and the principal DNA components are located in the nucleus and that the light DNA is in the cytoplasm. The light DNA comprises approximately 10% of the DNA. About – of the light DNA is synthesized during the S period, and the remainder is synthesized throughout G₂ (there is no G₁ in Physarum). The light DNA is metabolically stable. A low, variable level of incorporation of radioactive thymidine into the principal, nuclear DNA component was observed during G₂.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

• Allfrey, V. G., Johnson, E. M., Sun, I. Y.-C., Littau, V. C., Matthews, H. R., Bradbury, E. M. (1978). Structural Organization and Control of the Ribosomal Genes in Physarum. Cold Spring Harb Symp Quant Biol 42: 505-514 [Abstract]  

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents