The 2 micron plasmid of laboratory yeast strains is a type-1/type-2 hybrid.
Industrial yeast strains carry one of two homeologous 2 microns plasmids designated as type-1 or type-2. The 2 microns plasmid, Scp1, found in common laboratory strains of Saccharomyces cerevisiae is considered a type-2 plasmid, since the ori, STB, RAF and REP1 loci and intergenic sequences of the right-unique region of Scp1 are homologous to the corresponding loci in industrial strain type-2 plasmids. However, within both its 599 bp inverted repeats Scp1 has 142-bp sequences homologous to the bakers' yeast type-1 plasmid. DNA sequence analyses and oligonucleotide hybridizations indicate that the 142-bp insertion in Scp1 was probably due to homeologous recombination between type-1 and type-2 plasmids. These results suggest that some of the plasmid and chromosomal sequence polymorphisms seen in laboratory yeast strains result from homeologous recombination in their ancestral breeding stock.
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Department of Microbiology, University of Saskatchewan, Saskatoon, Canada.
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D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics; D005800:Genes, Fungal; D006824:Hybridization, Genetic; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics* / Q000648:ultrastructure; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D004271:DNA, Fungal