DNA from human tumor cells Isolation of the ras Transfect mouse 3T3 cells oncogene from human tumor cells Culture for 2 weeks Focus of transformed 3T3 cells growing among untransformed cells Extract DNA, transform new mouse cells Second cycle Extract genomic dNA Introduce into phage vector Surviving human dna Phage library 7S2S@GQQ@3 Plate phage on Alu probe igure by MIT OCW Replic filter paper OncogeneIsolation of the Ras oncogene from human tumor cells Figure by MIT OCW