CYP1A1 and cancer: A studied polymorphism in the CYP1A1 gene (located on chromosome 15, including 9 exons or chromosome 15q22–24) has been shown to be related to the cancer risk, known as CYP1A1 MspI polymorphism (CYP1A1*2A)18 that CYP1A1 MspI is a T → C transition placed downstream of exon 7, in 3′ noncoding region19.