The Desoxyribonucleic Acid of Interphase and Dividing Nuclei

Abstract

Classical genetics has associated the rigid transmission of hereditary characters with the constancy of the chromosome pattern. Modern work has shown that the chromosomes contain the substance desoxyribonucleic acid (DNA), which is believed to be the carrier of genetic potential. In general, the amount of this material present per cell is constant in all organs and tissues in a given species. Furthermore, isotopic work with a DNA precursor, phosphorus, showed that it does not enter the DNA of tissues in which the cells do not divide—a result interpreted as supporting the classical concept of the stability of genetic material. It was known, on the other hand, that phosphorus is incorporated into the DNA of tissues containing cells undergoing division—a result interpreted as being due to the synthesis of DNA associated with cell division. Evidence is presented to indicate that such synthesis does occur, but is far more extensive than was hitherto suspected, since it involves the complete replacement of all the DNA present before initiation of the cell division. How the cell can safeguard the stability of the genetic material in the course of this total DNA renewal can only be surmised at this time.

[14C]Formate labelling of bases of nucleic acids in respiring slices of rat tissues

“…Indeed, because of the possibility that non-radioactive DNA may be contaminated with traces of much more radioactive RNA, in vitro studies with 32p, such as those of DeLuca et al (1953) with brain slices and Kit, Bacila & Barron (1954) with lymphocytic cells, make it uncertain whether DNA is labelled at all. This would be in conformity with the suggestion that 32p is incorporated into DNA only during cell division (Marshak, 1941;Hull & Kirk, 1950; Osgood, Li, Tivey, Duerst & Seaman, 1951;Stevens, Daoust & Leblond, 1953).…”

Effect of 31 MeV Gamma and 200 kV Roentgen Whole-Body Irradiation on the Nucleic Acid Content of Mouse Tissues

“…Similar phenomena has also been noted in the case of RNA, where under equal conditions of irradiation certainly no depletion of RNA has been revealed in the liver, while the spleen showed a distinct diminution in the content of the substance. The responses of the three organs studied are not surprising in view of their different DNA renewal rate (5), (17), the postirradiation disturbance of which is more marked in organs with higher cell division rates.…”

Cell Cycle Regulation by Heat Shock Transcription Factors

“…Changes in cytoplasmic structures were also revealed in studies that took place over a short period, and structural changes of mitochondria, Golgi substance, new cell walls, mitotic spindles, and centromere were identified [ 9 , 10 , 11 , 12 , 13 , 14 ]. Classification into Gap1 (G 1 ), synthesis (S), Gap2 (G 2 ), and mitosis (M) phases was suggested following the observation of cytoplasmic structures [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”