A CMV promoter drives ubiquitous expression of a human KRAS minigene with a nucleotide substitution that results in the amino acid substitution of valine for glycine at position 12, an IRES, and EGFP. The minigene is preceded by a floxed neo cassette. Cre-mediated recombination is required to allow for expression of the Kras mutation that occurs in 40-50% of human colorectal adenomas and carcinomas. (J:122904)