Abstract
The molecular weight of single-stranded DNA from the slime mold Physarum polycephalum has been determined by alkaline gradient centrifugation. The average molecular weight during DNA synthesis (∼1.5 × 107 D) is less than that observed in nonsynthetic periods (∼4 × 107 D). On the basis of a chromosome number of 50 per nucleus and a DNA content of 1 μμg per nucleus, we are led to conclude that at pH 12 each chromosome dissociates into 300 (single-stranded) pieces of DNA. We have also compared the sedimentation profiles of single-stranded DNA from Escherichia coli, PPLO, and T2 bacteriophage. These data support the conjecture that each bacterial chromosome can be dissociated into 10 or 12 single-stranded pieces of DNA. Dissociation of DNA into multiple pieces under our experimental conditions is best interpreted in terms of interruptions in the continuity of the DNA either by naturally occurring gaps or at alkali-labile bonds.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- BURGI E., HERSHEY A. D. Sedimentation rate as a measure of molecular weight of DNA. Biophys J. 1963 Jul;3:309–321. doi: 10.1016/s0006-3495(63)86823-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- CAIRNS J. The bacterial chromosome and its manner of replication as seen by autoradiography. J Mol Biol. 1963 Mar;6:208–213. doi: 10.1016/s0022-2836(63)80070-4. [DOI] [PubMed] [Google Scholar]
- Kaplan H. S. DNA-strand scission and loss of viability after x irradiation of normal and sensitized bacterial cells. Proc Natl Acad Sci U S A. 1966 Jun;55(6):1442–1446. doi: 10.1073/pnas.55.6.1442. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MCGRATH R. A., WILLIAMS R. W., SETLOW R. B. INCREASED 3H-THYMIDINE INCORPORATION INTO DNA OF IRRADIATED SLIME MOULD. Int J Radiat Biol Relat Stud Phys Chem Med. 1964;8:373–380. doi: 10.1080/09553006414550441. [DOI] [PubMed] [Google Scholar]
- McGrath R. A., Williams R. W. Reconstruction in vivo of irradiated Escherichia coli deoxyribonucleic acid; the rejoining of broken pieces. Nature. 1966 Oct 29;212(5061):534–535. doi: 10.1038/212534a0. [DOI] [PubMed] [Google Scholar]
- STUDIER F. W. SEDIMENTATION STUDIES OF THE SIZE AND SHAPE OF DNA. J Mol Biol. 1965 Feb;11:373–390. doi: 10.1016/s0022-2836(65)80064-x. [DOI] [PubMed] [Google Scholar]