Abstract: The present invention relates to a method of producing a cell comprising a conditionally active transgene in its genome, the method comprising (a) introducing into the cell a targeting vector, wherein the targeting vector comprises (i) a 5? recombinase recognition site specifically recognised by a first recombinase, wherein the first recombinase is endogenously present in the cell or wherein the first recombinase or a nucleic acid molecule encoding said first recombinase in expressible form is introduced into the cell; followed by (ii) a 5? recombinase recognition site specifically recognised by a second recombinase, wherein the second recombinase is not endogenously present or is not active in the cell; followed by (iii) a selection cassette comprising a positively selectable marker gene; followed by (iv) a 3? recombinase recognition site specifically recognised by a third recombinase, wherein the third recombinase is not endogenously present or is not active in the cell; followed by (v) the transgene; follo

Abstract: The present invention relates to a novel class of gene trap vector (enhanced gene trap vectors, eGTV) for efficiently identifying silent or weakly expressed target genes in mammalian genomes, methods of their production and methods for identifying and mutating target genes by using the enhanced gene trap vectors. The gene trap vectors of the present invention can also be used for inducing the expression of silent genes and enhancing the expression of weakly expressed genes. The use of the enhanced gene trap vectors for creating transgenic organisms to identify gene function and to validate pharmaceutical compounds prior to clinical applications is a further aspect of the present invention.

Abstract: The present invention relates to a method of producing a cell comprising a conditionally active transgene in its genome, the method comprising (a) introducing into the cell a targeting vector, wherein the targeting vector comprises (i) a 5? recombinase recognition site specifically recognised by a first recombinase, wherein the first recombinase is endogenously present in the cell or wherein the first recombinase or a nucleic acid molecule encoding said first recombinase in expressible form is introduced into the cell; followed by (ii) a 5? recombinase recognition site specifically recognised by a second recombinase, wherein the second recombinase is not endogenously present or is not active in the cell; followed by (iii) a selection cassette comprising a positively selectable marker gene; followed by (iv) a 3? recombinase recognition site specifically recognised by a third recombinase, wherein the third recombinase is not endogenously present or is not active in the cell; followed by (v) the transgene; follo