Showing papers by "Thomas D. Petes published in 1974"
TL;DR: Characterisation of yeast DNA replication is similar to higher eukaryotic DNA replication in two important respects: first, most and possibly all initiations are internal, and many chromosomes contain more than one replication unit.
Abstract: THE study of replication in higher eukaryotes has been hampered by the large size of the DNA molecules in their chromosomes. The yeast Saccharomyces cerevisiae is a eukaryote with very little DNA per haploid nucleus (9 × 109 daltons)1. This has facilitated measurement of intact yeast chromosomal DNA by sedimentation velocity2 and electron microscopy3. The results indicate that yeast chromosomes are similar in size to those of viruses and bacteria, each chromosome containing a single DNA duplex ranging from 108 to 109 daltons. More than 95% of the chromosomal DNA molecules isolated from asynchronous cultures are simple linear structures, but the few branched structures are good candidates for replication intermediates3. We have used two experimental approaches which provide evidence that these exceptional molecules are, indeed, replication intermediates. Characterisation of these molecules by electron microscopy indicates that yeast DNA replication is similar to higher eukaryotic DNA replication in two important respects. First, most and possibly all initiations are internal. Second, many chromosomes contain more than one replication unit.
121 citations
TL;DR: The rate of DNA chain elongation and the distance between DNA synthesis initiation sites in senescent and control fibroblasts by DNA fibre autoradiography is examined.
Abstract: SINCE the demonstration that diploid human fibroblasts have a limited lifespan in culture1,2 and that the lifespan in culture is a function of the age of the donor2,3, many explanations of fibroblast ageing have been offered4. The production of error-containing enzymes by either an ‘error catastrophe’5,6 or somatic mutation has been suggested as one possible cause4,7. Errors in the enzymes which replicate the cellular DNA might have the gross effect of slowing the rate of DNA replication. Here we examine the rate of DNA chain elongation and the distance between DNA synthesis initiation sites in senescent and control fibroblasts by DNA fibre autoradiography.
79 citations
39 citations
TL;DR: In this report, nuclear DNA molecules from several DNA synthesis mutants which had been classified as DNA initiation or DNA propagation mutants on the basis of incorporation kinetics were examined with the electron microscope and provide independent criteria for the classification of DNA initiation and propagation mutants.
Abstract: As in higher eukaryotes1,2, the nuclear DNA of the simple eukaryote Saccharomyces cerevisiae is replicated from multiple internal initiation sites along the chromosome3–5. The very small size of the chromosomal DNA in yeast3,6,7 and the availability of temperature-sensitive DNA synthesis mutants8,9 make a detailed study of DNA replication easier in yeast than in most other eukaryotic systems. In this report, nuclear DNA molecules from several DNA synthesis mutants which had been classified as DNA initiation or DNA propagation mutants on the basis of incorporation kinetics were examined with the electron microscope. Our results provide independent criteria for the classification of DNA initiation and propagation mutants on the basis of the structure of the nuclear DNA at the restrictive temperature.
39 citations