Genetic duplications in bacteria and their relevance for genetic toxicology

Hoffmann, George

doi:10.1016/0027-5107(85)90107-1

Cited by 9 publications

(10 citation statements)

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“…A general strategy for the selection of illegitimate recombinants is to employ a reporter gene that is not expressed efficiently unless an activating rearrangement occurs. Such an approach has been used to select deletions (32) or tandem duplications (2,17) in the bacterial chromosome. A useful system must enable the screening of large numbers of cells and the rapid determination of the newly activated structures.…”

Section: Resultsmentioning

confidence: 99%

“…UV light forms mainly bulky lesions in DNA (e.g., pyrimidine dimers), H202 is a radiomimetic agent, and methylnitrosoguanidine methylates DNA bases and the phosphodiester chain (16). UV light (17,32) has been reported to increase the frequency of illegitimate recombinations in other systems, while H202 and methylnitrosoguanidine have evidently not been examined for this property.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, treatment of bacteria with UV light, X rays, or nitrous acid enhanced the production of gene duplications (17) or deletions (32), although the extent of recA involvement in these processes was not always measured. Treatment of eucaryotic cells with ionizing radiation increased the frequency of aberrant rearrangements (6).…”

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confidence: 99%

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Illegitimate recombination in an Escherichia coli plasmid: modulation by DNA damage and a new bacterial gene

Stearns

Demple

1988

J Bacteriol

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Illegitimate recombination in an Escherichia coli plasmid: modulation by DNA damage and a new bacterial gene

Stearns

Demple

1988

J Bacteriol

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“…This may be fast for enzymes like mammalian hemoglobins, but it is very easy to understand such a rate for haploid organisms under metabolic stress conditions. The major source of new genes under such conditions is gene duplication, which occurs under a wide variety of different environmental conditions (Hoffman 1985;Schimke et al 1986;Sonti and Roth 1989). Under starvation conditions, bacteria are known to undergo duplications of large segments of their genome.…”

Section: Size Increase Of Early Genomesmentioning

confidence: 99%

How long did it take for life to begin and evolve to cyanobacteria?

1994

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There is convincing paleontological evidence showing that stromatolite-building phototactic prokaryotes were already in existence 3.5 x 10(9) years ago. Late accretion impacts may have killed off life on our planet as late as 3.8 x 10(9) years ago. This leaves only 300 million years to go from the prebiotic soup to the RNA world and to cyanobacteria. However, 300 million years should be more than sufficient time. All known prebiotic reactions take place in geologically rapid time scales, and very slow prebiotic reactions are not feasible because the intermediate compounds would have been destroyed due to the passage of the entire ocean through deep-sea vents every 10(7) years or in even less time. Therefore, it is likely that self-replicating systems capable of undergoing Darwinian evolution emerged in a period shorter than the destruction rates of its components (<5 million years). The time for evolution from the first DNA/protein organisms to cyanobacteria is usually thought to be very long. However, the similarities of many enzymatic reactions, together with the analysis of the available sequence data, suggest that a significant number of the components involved in basic biological processes are the result of ancient gene duplication events. Assuming that the rate of gene duplication of ancient prokaryotes was comparable to today's present values, the development of a filamentous cyanobacterial-like genome would require approximately 7 x 10(6) years--or perhaps much less. Thus, in spite of the many uncertainties involved in the estimates of time for life to arise and evolve to cyanobacteria, we see no compelling reason to assume that this process, from the beginning of the primitive soup to cyanobacteria, took more than 10 million years.

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“…Tandem genetic duplications in bacteria occur at spontaneous frequencies that are typically greater than lop5 and higher than I % for some chromosomal regions Roth, 1977, 1981;Hoffmann, 1985Hoffmann, , 1992Petes and Hill, 19881. Most duplications arise by recombinational mechanisms that are dependent on homologous sequences and recA-gene function.…”

Section: Bacterial Assays For Studying Recombinagensmentioning

confidence: 99%

Induction of genetic recombination: Consequences and model systems

Hoffmann¹

1994

Environ. Mol. Mutagen.

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Radiation and many chemicals have been found to induce homologous genetic recombination. Experimental systems that allow the detection and characterization of recombinagens exist in organisms as diverse as bacteria, fungi, plants, insects, and mammals. Recombination plays an important role in many biological processes, and studies of recombinagens can provide insight into underlying mechanisms. Studies of recombinagens are also of applied interest in genetic toxicology, because recombinational events in somatic cells can contribute to human disease. Clear connections have been established between mitotic recombination and the etiology of some cancers. This article briefly reviews two aspects of the induction of genetic recombination by radiation and chemicals--the health implications of recombinagenic effects and assays for detecting recombinagens.

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Genetic duplications in bacteria and their relevance for genetic toxicology

Cited by 9 publications

References 64 publications

Illegitimate recombination in an Escherichia coli plasmid: modulation by DNA damage and a new bacterial gene

Illegitimate recombination in an Escherichia coli plasmid: modulation by DNA damage and a new bacterial gene

How long did it take for life to begin and evolve to cyanobacteria?

Induction of genetic recombination: Consequences and model systems

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