Patent ID: 7449179

Claim:
A genetically engineered vector comprising: a) a mutational element cassette comprising operably linked: i) a DNA comprising a first site-specific recombination sequence for a first recombinase; ii) a DNA comprising a mutational sequence which comprises a splice acceptor sequence linked to a first marker gene linked to a polyadenylation sequence; and iii) a DNA comprising a second site-specific recombination sequence for the first recombinase, wherein the first and second site-specific recombination sequences in a)i and a)iii are mutant sequences that are substrates for the first recombinase; and b) a gene trap cassette comprising operably linked: i) a DNA comprising a first site-specific recombination sequence for a second recombinase; ii) a DNA comprising a first gene trap element comprising a promoter operably linked to a second marker gene operably linked to a splice donor sequence and a second gene trap cassette comprising promoter operably linked to a unique sequence not present in the genome of a selected host cell; and iii) a DNA comprising a second site-specific recombination sequence for the second recombinase; wherein the gene trap cassette is 3′ to the mutational element cassette, wherein the first and second recombinases are different, wherein the DNA of a)i) and the DNA of a)iii) are in opposite orientation to each other, and wherein the DNA of b)i) and the DNA of b)iii) are in the same orientation, wherein if the vector inserts into an exon in the genome of the cell and is expressed, the unique sequence is present in a RNA transcript but if the vector inserts into an intron in the genome of the cell and is expressed, the unique sequence is not spliced into mRNA.