• Current Research on Agriculture and Life Sciences
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• v.5
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• pp.52-58
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• 1987

The yeast S. cerevisiae DBY747 was transformed with E. C - S. C shuttle vector YIp5, YEp13 and YRp7 by the method of spheroplast. The transformation frequency of YEp13 and YRp7 in S. cerevisiae DBY747 was $1.2{\times}10^3$ and $1.0{\times}10^2$ per $10{\mu}g$ of DNA, respectively. The transformants with YIp5 plasmid incapable of autonomous replication in S. cerevisiae were not detected in the condition of this experiment, but YIpS plasmid expressed the gene carried on it when cotransformed with a helper plasmid such as YEp13 or YRp7 : autonomously replicating plasmid. When plasmids were used in covalently closed circular form, cotransformation frequency of Ylp5-YEpl3 and Ylp5-YRp7 was 210 and 95 per $10{\mu}g$ of DNA, respectively. In cotransformation of linear plasmids, transformation frequency of the same cohesive ends was similar to that of noncomplementary cohesive ends. Transformants by the cotransformation with circular plasmids have been shown much higher frequency than with linear plasmids in S. cerevisiae DBY 747. The mitotic segregation stability test suggested that the cotransformant of YIpS-YEp13 was more stable than that of YIpS-YRp7.