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Biomedical subjects

B Futcher

Publications and source records attributed to B Futcher.

41 records · Page 3Linked to original sources
PubMed1988

Maintenance of the 2 micron circle plasmid of Saccharomyces cerevisiae by sexual transmission: an example of a selfish DNA.

Many eukaryotic mobile elements have been identified, but few have any obvious function. This has led to the proposal that many such elements may be parasitic DNA. We have used the 2 micron circle plasmid of Saccharomyces cerevisiae as a model system to investigate the maintenance of a cryptic genetic element. We find that under certain conditions this plasmid can spread through experimental populations despite demonstrable selection against it. This spread is dependent upon outbreeding, suggesting that cell to cell transmission of the plasmid during the yeast sexual cycle can counterbalance selection, and maintain the plasmid in populations. This result provides experimental support for the idea that some mobile elements may be parasitic DNA.

Crosses, Genetic↗
PubMed1986

Toxic effects of excess cloned centromeres.

Plasmids carrying a Saccharomyces cerevisiae centromere have a copy number of one or two, whereas other yeast plasmids have high copy numbers. The number of CEN plasmids per yeast cell was made artificially high by transforming cells simultaneously with several different CEN plasmids carrying different, independently selectable markers. Some host cells carried five different CEN plasmids and an average total of 13 extra copies of CEN3. Several effects were noted. The copy number of each plasmid was unexpectedly high. The plasmids were mutually unstable. Cultures contained many dead cells. The viable host cells grew more slowly than control cells, even in nonselective medium. There was a pause in the cell cycle at or just before mitosis. We conclude that an excess of centromeres is toxic and that the copy number of centromere plasmids is low partly because of selection against cells carrying multiple centromere plasmids. The toxicity may be caused by competition between the centromeres for some factor present in limiting quantities, e.g., centromere-binding proteins, microtubules, or space on the spindle pole body.

Cell Cycle↗
PubMed1984

Cloning of the vaccinia virus telomere in a yeast plasmid vector.

The vaccinia virus DNA telomere, which contains a covalently closed hairpin structure, has been cloned in a yeast plasmid vector. Restriction mapping indicates that the cloned vaccinia telomere is maintained in yeast not in its native hairpin configuration but as an inverted repeat structure, within a circular plasmid, with the sequences of the viral hairpin now at the axis of symmetry of an imperfect palindrome. As such, the cloned telomere resembles the telomeric replicative intermediate observed during vaccinia virus DNA replication. Small deletions and duplications in the viral inverted repeats of different clones suggest a model in which the observed circular plasmids were generated in yeast by the replication of hybrid linear DNA molecules consisting of the linearized yeast vector flanked by two hairpin-containing vaccinia termini.

Cloning, Molecular↗