| organization of a chinese hamster ovary dihydrofolate reductase gene identified by phenotypic rescue. | we have constructed a genomic dna library from a methotrexate-resistant chinese hamster ovary cell line (choc 400) in the cosmid vector phc79. by utilizing a murine dihydrofolate reductase (dhfr) cdna clone, we have identified 66 dhfr+ clones among the 11,000 colonies screened by colony hybridization. to isolate a recombinant cosmid containing the entire dhfr gene, we have tested these colonies for their ability to rescue a dhfr- chinese hamster ovary cell line, using the spheroplast fusion meth ... | 1983 | 6310370 |