DNA Repair and UV Mutagenesis in Escherichia Coli PDF Download
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Languages : en
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The subject of this thesis is repair of DMA damage in bacteria caused by ultraviolet irradiation and the errors made during this repair. In particular the study centred on post-replication repair. Two different approaches were used. First, genetical methods were used to study the effect of UV irradiation on mutation under varied conditions. Secondly, biochemical methods were used to examine changes in newly synthesized DNA under the same conditions. Thus, an attempt was made to correlate changes in the DNA with genetical changes. A survey of the most relevant literature is given in Chapter 1. Chapter 2 discusses materials and methods used. The rest of the thesis deals with results of experimental work. In Chapter 3 the effects of different post-irradiation treatments on mutation and repair are examined. The main conclusion is that the mutation enhancement caused by adding broth or acriflavine to post-irradiation medium cannot be entirely due to an effect on excision repair. In Chapter 4 a comparison is made between repair in excision deficientand excision proficient bacteria after low doses of UV irradiation. In Chapter 5 the relationship between the filling of daughter strand gaps and mutation fixation in an excision deficient strain is examined. It was discovered that under certain well-defined conditions gap filling was error-free. The sixth chapter deals with mutation frequency decline, or MFD. It was found that MFD could occur both pre- and post-replicatively and could thus not be explained solely as an effect on pre-replicative excision.
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Languages : en
Pages :
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Book Description
The subject of this thesis is repair of DMA damage in bacteria caused by ultraviolet irradiation and the errors made during this repair. In particular the study centred on post-replication repair. Two different approaches were used. First, genetical methods were used to study the effect of UV irradiation on mutation under varied conditions. Secondly, biochemical methods were used to examine changes in newly synthesized DNA under the same conditions. Thus, an attempt was made to correlate changes in the DNA with genetical changes. A survey of the most relevant literature is given in Chapter 1. Chapter 2 discusses materials and methods used. The rest of the thesis deals with results of experimental work. In Chapter 3 the effects of different post-irradiation treatments on mutation and repair are examined. The main conclusion is that the mutation enhancement caused by adding broth or acriflavine to post-irradiation medium cannot be entirely due to an effect on excision repair. In Chapter 4 a comparison is made between repair in excision deficientand excision proficient bacteria after low doses of UV irradiation. In Chapter 5 the relationship between the filling of daughter strand gaps and mutation fixation in an excision deficient strain is examined. It was discovered that under certain well-defined conditions gap filling was error-free. The sixth chapter deals with mutation frequency decline, or MFD. It was found that MFD could occur both pre- and post-replicatively and could thus not be explained solely as an effect on pre-replicative excision.
Author: Errol C. Friedberg
Publisher: American Society for Microbiology Press
ISBN: 1555813194
Category : Science
Languages : en
Pages : 2587
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An essential resource for all scientists researching cellular responses to DNA damage. • Introduces important new material reflective of the major changes and developments that have occurred in the field over the last decade. • Discussed the field within a strong historical framework, and all aspects of biological responses to DNA damage are detailed. • Provides information on covering sources and consequences of DNA damage; correcting altered bases in DNA: DNA repair; DNA damage tolerance and mutagenesis; regulatory responses to DNA damage in eukaryotes; and disease states associated with defective biological responses to DNA damage.
Author: Martinus R. Schaaper
Publisher:
ISBN:
Category :
Languages : en
Pages : 106
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Author: W. Generoso
Publisher: Springer Science & Business Media
ISBN: 1468438425
Category : Medical
Languages : en
Pages : 450
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Not many years ago most discussion of mutation induction by physical and chemical agents concentrated on the initial lesions induced in the DNA with the implicit assumption that once the lesions were made they were converted almost automatically to mutations by relatively simple processes associated with DNA replication. The discovery of a variety of enzymatic processes that can repair these lesions, the great increase in our understanding of the molecular steps involved in repair, replication, and recombination, and the increasing availability of cells with genetic defects in these pro cesses have led to the realization that mutation induction is a far more complex process than we originally thought. Repair systems can remove lesions before they can be converted to mutation, they can also convert initial lesions to secondary ones that are them selves mutagenic, and they can remove potentially lethal lesions at the expense of making mutations. The error-avoiding systems asso ciated with replication are themselves complex and may be caused to make mistakes in various ways. These different pathways for mutation production and mutation avoidance are still being worked out in prokaryotes and are less well understood in eukaryotes. This symposium shows, however, that very encouraging progress has been made in the last several years, and the progress is now accelerating.
Author: Bradley Theodore Smith
Publisher:
ISBN:
Category : Press
Languages : en
Pages : 316
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All organisms face constant challenges to the integrity of their genomes, from environmental agents such as ultraviolet light (UV) to errors generated by their own DNA polymerases. To deal with these challenges, all organisms possess a range of DNA repair and damage tolerance systems. In bacteria, there exists an inducible response to DNA damage termed the SOS response, in which damage induces the expression of greater than forty genes involved in repair. Mismatch repair (MMR) is a system by which the cell is able to avoid mutations by correcting DNA replication errors. Working with living Bacillus subtilis cells, the studies described here have found that MutS and MutL, the key proteins of MMR, form discrete foci in response to mismatches. These MMR foci are the active sites of repair, and appear to assemble near the DNA polymerase at mismatched base-pairs. This is consistent with a model in which the newly-synthesized DNA strand containing the error is discriminated from the parental strand via interactions between MMR proteins and the replisome.
Author: Andrei Kuzminov
Publisher: Landes Bioscience
ISBN:
Category : Medical
Languages : en
Pages : 234
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Author: J. Lemontt
Publisher: Springer Science & Business Media
ISBN: 1461334764
Category : Science
Languages : en
Pages : 391
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It has been nearly 35 years since the peacetime Biology Division of Oak Ridge National Laboratory was started, born of rather inauspicious conditions. Virtually no facilities were available and most of the wartime scientists had left. So, when we started out, it was obvious to me that something had to be done to reestab lish research. Even more, because Oak Ridge was not known at that time for its biological work but rather for the separation of Uranium 235, nuclear reactor development, and radioisotope produc tion, a new tradition had to be promoted. Although good biological work had been done at Oak Ridge during the war to protect the workers and the results of this work were quite excellent, very few installations remained. When we started the work of the Biology Division, it became essential to make it part of the flow of mod~rn biology allover the world. As Director, I had to do more than just attract promising scientists. We created an atmosphere conducive to creative research and nurtured all of the other aspects of a productive laboratory. Of course, we carefully prepared the results of our work in publish able form. We made a sincere effort to invite seminar speakers and lecturers to come to Oak Ridge despite the sacrifices this presented to our early budget. We also had to do something more, and here I "cashed in" on my experience of the previous 15 years.
Author: David Bramhill
Publisher:
ISBN:
Category :
Languages : en
Pages : 140
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Author: Philip Hanawalt
Publisher: Springer Science & Business Media
ISBN: 1468428950
Category : Science
Languages : en
Pages : 433
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An "age" has passed in the 40 years since we first observed recovery from radiation damage in irradiated bacteria. During the early 1930s, we had been discussing the possibility of rapid changes after radiation exposure with Farring ton Daniels, Benjamin Duggar, John Curtis, and others at the University of Wisconsin. After working with living cells, we had concluded that organisms receiving massive insults must have a wide variety of repair mechanisms available for restoration of at least some of the essential properties of the cell. The problem was how to fmd and identify these recovery phenomena. At that time I was working on a problem considered to be of great importance-the existence of the so-called mitogenetic rays. Several hundred articles and a score of books had already appeared dealing with mitogenetic rays, a type of radiation that was thought to exist in the shorter ultraviolet region. Our search for mitogenetic rays necessitated the design of experiments of greatest sensitivity for the detection of ultraviolet. It was vital that conditions be kept as constant as possible during exposure. All the work was done at icewater temperature (3-5°C) during and after exposure. We knew that light was an important factor for cell recovery, so all our experiments were done in dim light, with the plated-out cells being covered with dark cloth. Our statements on the effect of visible light stimulated Kelner to search for "photoreactivation' (as it was later called).
Author: Helen Joy Bates
Publisher:
ISBN:
Category :
Languages : en
Pages :
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