A DNA fragment containing the ADE2 gene from Schwanniomyces occidentalis can be maintained as an extrachromosomal element.
A 4.05-kb DNA fragment containing the ADE2 gene from Schwanniomyces occidentalis was cloned into the pUC19 vector. When an ade2 strain of Sc. occidentalis was transformed with this plasmid, pADE-2 was found to integrate into the host chromosome and was also present in a variety of extrachromosomal species. These extrachromosomal elements were present in multiple copies, varied in molecular mass and were composed of polymerized forms of pADE-2. A fragment containing the ADE2 gene was used to transform a Sc. occidentalis ade2 mutant, as either a linear or circularized molecule. The linear form integrated into the host genome, whereas the circularized form was found as a stably maintained extrachromosomal element with no evidence of integration or detectable loss of the Ade+ phenotype upon subculturing of transformed yeast under nonselective conditions for 60 generations. The ratio of the number of extrachromosomal ADE2 genes to genomic ADE2 ranged from 3.8 to 6.6.
Klein
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Molecular Biology Research, Upjohn Company, Kalamazoo, MI 49007.
Favreau
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D015139:Blotting, Southern; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics*; D005800:Genes, Fungal; D010641:Phenotype; D010957:Plasmids; D015183:Restriction Mapping; D004718:Saccharomycetales / Q000235:genetics*; D014170:Transformation, Genetic
D004271:DNA, Fungal