Genetically modified somatic cells of a non human animal are provided that are engineered to contain a self excisable recombinase expression cassette comprising a site specific recombinase gene operably linked to an ES cell specific promoter. Compositions and methods for producing a genetically modified cloned non human animal that is free of a selective marker gene and a recombinase gene are provided wherein a targeting construct comprising a self excisable recombinase gene operably linked to an ES cell specific promoter is introduced into differentiated somatic cells. The genetically modified genome of the somatic cells is transferred into an enucleated host oocyte. The artificially created zygote is then cultured until the blastocyst embryonic stage and subsequently implanted into a uterus of a surrogate mother to form a genetically modified cloned non human animal free of selective marker and recombinase genes.
