Additionally, inheritance of the DBA/2 allele of four of these loci (Psl1.1a, Psl1.2a, Psl1.2b, Gsta4) results in increased sensitivity whereas inheritance of the DBA/2 allele of two loci (Psl1.1b, Psl1.2c) results in decreased sensitivity to skin tumor promotion. The gene discussed is GSTA4; the disease is skin neoplasm.