> Chromosomal evolution in Saccharomyces
> G. FISCHER*, S. A. JAMES, I. N. ROBERTS, S. G. OLIVER & E. J. LOUIS*
> * Department of Biochemistry, University of Oxford, South Parks Road, Oxford
> OX1 3QU, UK
> National Collection of Yeast Cultures, Institute of Food Research, Norwich
> Research Park, Colney, Norwich NR4 7UA, UK
> School of Biological Sciences, University of Manchester, 2.205 Stopford
> Building, Oxford Road, Manchester M13 9PT, UK
> Recent issue of Nature
> Correspondence and requests for materials should be addressed to E.J.L.
> (e-mail: elouis at molbiol.ox.ac.uk).
>> The chromosomal speciation model invokes chromosomal rearrangements as the
> primary cause of reproductive isolation1. In a heterozygous carrier,
> chromosomes bearing reciprocal translocations mis-segregate at meiosis,
> resulting in reduced fertility or complete sterility. Thus, chromosomal
> rearrangements act as a post-zygotic isolating mechanism. Reproductive
> isolation in yeast is due to post-zygotic barriers, as many species mate
> successfully but the hybrids are sterile2, 3. Reciprocal translocations are
> thought to be the main form of large-scale rearrangement since the hypothesized
> duplication of the whole yeast genome 108 years ago4, 5. To test the
> chromosomal speciation model in yeast, we have characterized chromosomal
> translocations among the genomes of six closely related species in the
> Saccharomyces 'sensu stricto' complex6. Here we show that rearrangements have
> occurred between closely related species, whereas more distant ones have
> colinear genomes. Thus, chromosomal rearrangements are not a prerequisite for
> speciation in yeast and the rate of formation of translocations is not
> constant. These rearrangements appear to result from ectopic recombination
> between Ty elements or other repeated sequences.
> Available in PDF format on request
Read your mail with intest. Would have a pdf file, sent by yours, if possible.