« Previous AbstractKinetics of oligomer-forming reactions involving the major functional groups present in atmospheric secondary organic aerosol particles    Next AbstractGlobal alterations in chromatin accessibility associated with loss of SIN4 function »

Genet Res

Title:		"Masking and purging mutations following EMS treatment in haploid, diploid and tetraploid yeast (Saccharomyces cerevisiae)"
Author(s):		Mable BK; Otto SP;
Address:		"Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. bmable@uoguelph.ca"
Journal Title:		Genet Res
Year:		2001
Volume:		77
Issue:		1
Page Number:		9 - 26
DOI:		10.1017/s0016672300004821
ISSN/ISBN:		0016-6723 (Linking)
Abstract:		"The yeast, Saccharomyces cerevisiae, was used as a model to investigate theories of ploidy evolution. Mutagenesis experiments using the alkylating agent EMS (ethane methyl sulphonate) were conducted to assess the relative importance that masking of deleterious mutations has on response to and recovery from DNA damage. In particular, we tested whether cells with higher ploidy levels have relatively higher fitnesses after mutagenesis, whether the advantages of masking are more pronounced in tetraploids than in diploids, and whether purging of mutations allows more rapid recovery of haploid cells than cells with higher ploidy levels. Separate experiments were performed on asexually propagating stationary phase cells using (1) prototrophic haploid (MAT alpha) and diploid (MATa/alpha) strains and (2) isogenic haploid, diploid and tetraploid strains lacking a functional mating type locus. In both sets of experiments, haploids showed a more pronounced decrease in apparent growth rate than diploids, but both haploids and diploids appeared to recover very rapidly. Tetraploids did not show increased benefits of masking compared with diploids but volume measurements and FACScan analyses on the auxotrophic strains indicated that all treated tetraploid strains decreased in ploidy level and that some of the treated haploid lines increased in ploidy level. Results from these experiments confirm that while masking deleterious mutations provides an immediate advantage to higher ploidy levels in the presence of mutagens, selection is extremely efficient at removing induced mutations, leading growth rates to increase rapidly over time at all ploidy levels. Furthermore, ploidy level is itself a mutable trait in the presence of EMS, with both haploids and tetraploids often evolving towards diploidy (the ancestral state of S. cerevisiae) during the course of the experiment"
Keywords:		"Cell Division/drug effects Cell Separation Chromosome Deletion DNA/*drug effects DNA Damage Dose-Response Relationship, Drug *Ethyl Methanesulfonate Evolution, Molecular Flow Cytometry Gene Deletion Genes, Fungal/genetics Genes, Mating Type, Fungal Genoty;"
Notes:		"MedlineMable, B K Otto, S P eng Research Support, Non-U.S. Gov't England 2001/03/31 Genet Res. 2001 Feb; 77(1):9-26. doi: 10.1017/s0016672300004821"