Patent ID: 6855545

Claim:
A library of cultured eucaryotic cells comprising at least two subpopulations of cells, wherein the at least two subpopulations of cells comprises (a) a first subpopulation of cells, wherein cells of the first subpopulation have a first vector integrated nonspecifically into their genomes, wherein the first vector mediates the splicing of a foreign exon internal to a cellular transcript, and wherein the first vector comprises: (i) a foreign exon, (ii) a splice acceptor site operatively positioned 5′ to said foreign exon, and (iii) a splice donor site operatively positioned 3′ to said foreign exon, wherein the first vector does not comprise a promoter operatively positioned 5′ to said foreign exon; and (b) a second subpopulation of cells, wherein cells of the second subpopulation have a second vector integrated nonspecifically into their genomes, wherein the second vector mediates the splicing of a foreign exon 5′ to an exon of a cellular transcript, and wherein the second vector comprises: (i) a foreign exon, (ii) a promoter operatively positioned 5′ to said foreign exon, (iii) a splice donor site operatively positioned 3′ to said foreign exon; and (iv) a mutagenic foreign polynucleotide sequence located upstream from said promoter.