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P.208 right column 2nd paragraph: "Yeast episomal plasmids (YEps) are based on sequences from a natural yeast plasmid. This plasmid is present in most wild-type and laboratory S. cerevisiae strains and has a length of 6318 bp (Hartley and Donelson, 1980). Alluding to its contour size, it was termed 2μm or 2μ plasmid (Stevens and Moustacchi, 1971, Guerineau et al., 1971). The plasmid is cryptic, as it is not associated with any apparent phenotype and confers no selective advantage to its host cell, nevertheless, its loss is very rare (Futcher and Cox, 1983). The 2μ plasmid persists in yeast cells with 40–80 copies per haploid genome (primary sources). The plasmid copies are not homogeneously distributed in the nucleus, but are found in a few clusters (Scott-Drew and Murray, 1998, Velmurugan et al., 2000)." P.210 right column 3rd paragraph: "YEps containing the complete 2μ sequence achieve 40–80 copies per cell, which is comparable to the endogenous 2μ plasmid copy number (primary source Futcher and Cox, 1984)." |