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Biomedical subjects

B J Kilbey

Publications and source records attributed to B J Kilbey.

At least 37 records · Page 2Linked to original sources
PubMed1979

The mutagenic potential of unexcised pyrimidine dimers in Saccharomyces cerevisiae, rad1-1: evidence from photoreactivation and pedigree analysis.

Photoreactivation and pedigree analysis have been combined to show that unexcised pyrimidine dimers in the DNA of rad1-1 yeast can initiate mutagenesis after passing through several DNA replications. Monomerisation of dimers immediately before the second replication to follow UV has no effect on mutants appearing after the first post-UV cell division but reduces second-generation mutants to one third of their frequency in the dark and has a similar through slightly less marked effect on mutants appearing in the third or subsequent generations. The bearing of these findings on the mechanism of UV mutagenesis is dicussed.

DNA↗
PubMed1977

Mutation in continuous cultures of Schizosaccharomyces pombe. I. Dependence of the kinetics of mutation accumulation upon the growth-limiting nutrilite.

The rate of spontaneous mutation to resistance to the 12,13-epoxytrichothecene trichodermin has been determined under different growth limiting conditions in continuous cultures of the microbial eukaryote Schizosaccharomyces pombe. In agreement with data obtained in bacterial systems by previous workers the kinetics observed for the accumulation of mutations is found to be dependent upon the nutrient used to limit the growth of the population. Under conditions of glucose-limitation mutation accumulation is directly proportional to the rate of cell division, while under histidine-limitation it is proportional to chronological time. Various possible explanations for these observations are discussed.

Ascomycota↗
PubMed1977

The timing of UV mutagenesis in yeast: a pedigree analysis of induced recessive mutation.

The mechanism of UV-induced mutation in eukaryotes was studied in individual yeast cells by a procedure that combined pedigree analysis and tetrad analysis. The technique involved the induction of recessive lethals and semilethals in G1 diploid cells. Induced frequencies were 25 and 61 percent at survival levels of 90 and 77 percent, respectively. No evidence of gross chromosome aberrations was detected. Recessive mutations that affect only one strand or that affect both strands of the DNA molecule are induced much at random among a population of cells, and both types can occur within the same cell. However, the data confirm that two-strand mutations are in the majority after a low level of irradiation. The simplest explanation involves a mechanism whereby most mutations are fixed in both strands prior to the first round of post-irradiation DNA replication. The recessive mutational consequences of irradiation are exhausted at the conclusion of the first post-irradiation cell division, although dominant-lethal sectoring continues at a high level through the second post-irradiation division. It is concluded that pyrimidine dimers that persist to the second round of DNA replication are rare or ineffective.

Cell Division↗
PubMed1975

Mutagenicity assays on fluorescent whitening agents using microorganisms.

Six fluorescent whitening agents (FWAs) have been re-examined for their activity as inducers of cytoplasmic petite mutants and mitotic gene conversion in diploid yeast Saccharomyces cerebisiae and reversion from auxotrophy to prototrophy in Neurospora crassa, Escherichia coli and Salmonella typhimurium. The results provide no indication that the FWAs examinded produce mutagenic changes or any other alterations in the gene material. In a recent re-examination with Salmonella using the method of Ames et al., the four examined compounds failed to elicit a mutagenic response in the presence of rat liver postmitochondrial supernatant and cofactors.

Biphenyl Compounds↗
PubMed1974

The modifying effects of strain and age on the mutagenic specificity of ultraviolet light in Neurospora crassa.

Two derivatives of K3/17 ad-3A 38701; inos 37401 of Neurospora crassa are described which show opposite specific reversional responses to UV. Both derivatives carry the same two auxotrophic alleles and appear to differ only in a single gene which influences the pattern of mutagen specificity. The differences between the derivatives only develop after the cultures have been aged for two to four weeks. Various possible explanations are considered.

Mutation↗