Xie Y, Pelcher L E, Rank G H
Department of Biology, University of Saskatchewan, Saskatoon, Canada.
J Mol Evol. 1994 Apr;38(4):363-8. doi: 10.1007/BF00163153.
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.
