Sequences from the 5' end of the Moloney murine leukemia virus were linked to a tyrosinase minigene consisting of a 2.1-kb promoter linked to a 1.9-kb tyrosinase cDNA. Expression of the tyrosinase minigene leads to melanin synthesis in the skin and fur. The transgene inserted in the non-coding region between Gm732 and Brwd3 on chromosome X. PCR amplification with minigene-only primer sets suggests that at minimum 2 copies inserted in tandem, while Southern blot hybridization indicates a maximum of 4 copies inserted together. Expression of Fam46d, located near the site of transgenic intergration, is upregulated. (J:167614)