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At least 1,711 records · Page 95Linked to original sources
PubMed1965

UNSTABLE GENETIC TRANSFORMATION IN BACILLUS SUBTILIS AND THE MODE OF INHERITANCE IN UNSTABLE CLONES.

Iyer, V. N. (Canada Department of Agriculture, Ottawa, Ont., Canada). Unstable genetic transformation in Bacillus subtilis and the mode of inheritance in unstable clones. J. Bacteriol. 90:495-503. 1965.-An ultraviolet-induced mutant has been isolated from the double auxotroph of Bacillus subtilis (bearing the linked mutations try(2) and his(2)). This mutant has the property of yielding unstable transformants which, in the case of transformation to prototrophy, can be recognized by reduced colony size on minimal agar. Unstable transformant clones usually become stabilized early during the development of the clone (within 12 generations). Analyses of genotypes emerging from such clones on stabilization indicate that in some of these clones the exogenote is transmitted linearly; its integrity is sufficiently preserved that it can participate in two independent recombination events in two different cells. Genetic markers on the exogenote are expressed in situations where genetic integration has not occurred.

Bacillus subtilis↗
PubMed1963

ULTRAVIOLET IRRADIATION OF NATIVE AND DENATURED TRANSFORMING DEOXYRIBONUCLEIC ACID FROM HAEMOPHILUS INFLUENZAE.

Cabrera-Juarez, Emiliano (Johns Hopkins University School of Hygiene and Public Health, Baltimore, Md.) and Roger M. Herriott. Ultraviolet irradiation of native and denatured transforming deoxyribonucleic acid from Haemophilus influenzae. J. Bacteriol. 85:671-675. 1963.-Two antibiotic-resistance markers in denatured deoxyribonucleic acid (DNA) from Haemophilus influenzae showed about the same sensitivity to ultraviolet irradiation as in native DNA. The resistance of markers in denatured DNA to ultraviolet (UV) light increases with alkalinity up to pH 12. New transforming markers or genetic "lethals" were not produced by in vitro irradiation of either native or denatured DNA. The UV irradiation of the denatured DNA reduces its capacity to form new markers with nitrous acid. Nitrous acid reactivated some of the intrinsic marker destroyed by UV irradiation of denatured transforming DNA.

DNA↗
PubMed1990

Mechanistic studies of ionizing radiation and oxidative mutagenesis: genetic effects of a single 8-hydroxyguanine (7-hydro-8-oxoguanine) residue inserted at a unique site in a viral genome.

T4 RNA ligase was used to construct a deoxypentanucleotide containing a single 8-hydroxyguanine (7-hydro-8-oxoguanine; G8-OH) residue, which is one of the putatively mutagenic DNA adducts produced by oxidants and ionizing radiation. The pentamer d(GCTAG8-OH)p was prepared by the ligation of a chemically synthesized acceptor molecule, d(GCTA), to an adducted donor, 8-hydroxy-2'-deoxyguanosine 5',3'-bisphosphate. The acceptor was efficiently converted to the reaction product (greater than 95%), and the final product yield was 50%. Following 3'-dephosphorylation, the pentamer was characterized by UV spectroscopy, by high-pressure liquid chromatography, and by gas chromatography-mass spectrometry of the nucleosides released by enzymatic hydrolysis. Both d(GCTAG8-OH) and an unmodified control were 5'-phosphorylated by using [gamma -32P]ATP and incorporated covalently by DNA ligase into a five-base gap at a unique NheI restriction site in the otherwise duplex genome of an M13mp19 derivative. The ligation product contained G8-OH at the 3' residue of an in-frame amber codon (5'-TAG-3') (genome position 6276) of the phage lacZ alpha gene. The adduct was part of a nonsense codon in a unique restriction site in order to facilitate the identification and selection of mutants generated by the replication of the modified genome in Escherichia coli. Both control and adducted pentamers ligated into the genome at 50% of the maximum theoretical efficiency, and nearly all (approximately 90%) of the site-specifically adducted products possessed pentanucleotides that were covalently linked at both 5' and 3' termini. The G8-OH lesion in the NheI site inhibited the cleavage of the site by a 200-fold excess of NheI.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

Induction of micronuclei by bleomycin in G0 human lymphocytes: II. Potentiation by radioprotectors.

Dimethylsulfoxide (DMSO) and WR-1065 are radioprotectors, in that they reduce the effectiveness with which ionizing radiation causes genetic damage. Unlike their protective effects with radiation, these agents potentiate the induction of micronuclei by bleomycin in the cytokinesis-block assay in G0 human lymphocytes. High concentrations of DMSO (1 M) are required to cause potentiation. In contrast, WR-1065 causes dose-dependent potentiation at relatively low concentrations (1.25 to 10 mM). Cytogenetic analysis supports the results from the micronucleus assay, showing higher levels of genetic damage induced by the combination of bleomycin with DMSO or WR-1065 than by bleomycin alone. Possible mechanisms of potentiation are proposed.

Adult↗