Showing papers on "genomic DNA published in 1973"

Multiplicity of ribosomal RNA genes in Vicia species with different nuclear DNA contents.

Abstract: THERE is widespread variation between species of higher plants in amounts of nuclear DNA. In ten species a fifty-seven-fold variation in amounts of DNA per nucleus for equivalent cells was recorded1 and later reports showed wide ranges in the DNA contents of diploid species within single families (forty-fold in the Ranunculaceae2 and sixty to eighty-fold in the Droseraceae3). Most strikingly, large differences exist within a single genus between species with the same diploid chromosome number, for example, a three-fold range in the genus Lathyrus4 and between five and seven times as much nuclear DNA in Vicia faba as in V. sativa5–7. The structural basis of these variations is unclear although models of either a single stranded chromosome, in which DNA content increases by longitudinal multiplication of DNA sequences, or a multi-stranded chromosome, where increase is by lateral increase of strands, have been suggested (see reviews, refs 8, 9).

DNA Complementary to Ribosomal RNA: Relation between Genomic Proportion and Ploidy.

Abstract: Ten Nicotiana species were assayed for the proportion of DNA that is complementary to ribosomal RNA. This proportion varies from 0.27 to 0.9 percent, with tetraploid species having lower values than the diploid species. The tetraploid species have about twice as much DNA per cell as do diploid species. Thus, the absolute number of genes for ribosomal RNA varies less than the proportion of complementary DNA. Further, the number of genes for the RNA in 80S ribosomes varies less among species than does that for the RNA in 70S ribosomes. The data indicate that loss of DNA complementary to ribosomal RNA is associated with tetraploidy in the genus Nicotiana.

The transcription and state of herpes simplex virus DNA in productive infection and in human cervical cancer tissue.

Abstract: Summary We are reporting on the transcriptional program of herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) in productive infection in human epidermoid (HEp-2) cells and on the transcription and the stat eof HSV-2 DNA in a human cervical tumor. Our results may be summarized as follows. In productive infection, a total of 48% of HSV-1 DNA is transcribed. Analysis of the transcripts shows two kinds of controls. “Off-on” control of transcription is evident from the fact that early, before the onset of viral DNA synthesis, the transcripts arise from 44% of the DNA whereas late in infection the transcripts present in the infected cell arise from 48% of the DNA. The extent of transcription of the HSV-1 DNA early in infection is not affected by cycloheximide, an inhibitor of protein synthesis. Control of RNA abundance is evident from the observation that the transcripts present both early and late in infection form two classes differing in molar ratios. The abundant RNA is complementary to 14 and 19% of viral DNA early and late in infection, respectively, whereas the scarce RNA is complementary to 30 and 28%, respectively, of the DNA at the same time intervals. Several lines of evidence suggest that the abundant RNA specifies structural proteins of the virus. The transcriptional program of HSV-2 DNA differs from that of HSV-1 DNA in two respects. First, the amount of DNA transcribed early and late in infection corresponds to 21 and 50%, respectively. Second, while the viral RNA present late in infection also forms two classes differing in abundance, that present early in infection forms only one abundance class. Cycloheximide does affect transcription of HSV-2 DNA in that in the presence of the drug 45% of viral DNA is transcribed by 2 hr postinfection indicating that at least one “off-on” control of transcription is mediated by protein synthesis. HSV-1 and HSV-2 DNA9s share in common approximately 50% of their sequences with good matching of base pairs. Analysis of the transcription of the DNA sequences shared in common indicates that they are about evenly distributed among the templates for abundant and scarce RNA. However, the common sequences form 71% of the total sequences specifying abundant RNA and only 39% of the sequences specifying scarce RNA. A cervical tumor free of virus or viral antigen was analyzed by DNA-RNA hybridization techniques for the presence of viral RNA transcripts. The cervical tumor contained viral RNA transcripts complementary to 5% of HSV-2 DNA, and preliminary studies show that they correspond to both early and late transcripts. Analysis of the cervical DNA for the presence of HSV-2 DNA sequences led to three conclusions, i.e., first, only a fragment representing 40% of HSV-2 DNA was present; second, the fragment was present at concentrations of 1 mole/mole of cell DNA and, third, at least parts of this fragment are covalently linked to host DNA.

Synthesis and characterization of amplified DNA in oocytes of the house cricket, Acheta domesticus (Orthoptera: Gryllidae).

Abstract: At a time in the life cycle when a large proportion of the oocytes of Acheta incorporate 3H-thymidine into an extrachromosomal DNA body, synthesis of a satellite or minor band DNA, the density of which is greater than main band DNA, is readily detected. Synthesis of the satellite DNA is not detectable in tissues, the cells of which do not have a DNA body, or in ovaries in which synthesis of extrachromosomal DNA by the oocytes is completed. The DNA body contains the amplified genes which code for ribosomal RNA. However, less than 1 percent of the satellite DNA, all of which appears to be amplified in the oocyte, is complementary to ribosomal 18S and 28S RNA. In situ hybridization demonstrates that non-ribosomal elements, like the ribosomal elements of the satellite DNA, are localized in the DNA body.

Extrachromosomal DNA in Bacteria

Abstract: In addition to chromosomal DNA carrying the genetic information of the cell, many bacterial cells contain smaller circular DNA factors known as plasmids or episomes. These genetic elements endow the cell with additional biochemical capabilities. The fertility factors (F and F′), the antibiotic resistance factors (R), the colicinogenic factors (Col), the hemolytic factors (Hly), and other extrachromosomal DNA systems are described. These small DNA molecules can be isolated, and are therefore particularly suitable for the investigation of DNA replication and the stable establishment of genetic material in the bacterial cell.