Chimeric evolution of the 2-microns genome in Saccharomyces cerevisiae.
We compared the nucleotide substitution pattern over the entire genome of two unique variants of the 6,300-bp selfish DNA (2 microns) plasmid in Saccharomyces cerevisiae. The DNA sequence of the left-unique region is identical among 2-microns variants, while the right-unique region shows substantial divergence. This chimeric pattern cannot be explained by neutral or Darwinian selection models. We propose that horizontal transmission of the 2-microns plasmid coupled with a directed, polarized gene conversion maintains the DNA sequence of the left-unique region, whereas the right-unique region is subject to random drift and Darwinian selection.
Xie
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Department of Biology, University of Saskatchewan, Saskatoon, Canada.
Pelcher
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D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics*; D014644:Genetic Variation; D016681:Genome, Fungal; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010957:Plasmids / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D017422:Sequence Analysis, DNA
D004271:DNA, Fungal