The aryl hydrocarbon hydroxylase (Ah) locus and a novel restriction-fragment length polymorphism (RFLP) are located on mouse chromosome 12.

The aryl hydrocarbon hydroxylase (Ah) locus that controls the induction of chemical carcinogen-metabolizing enzymes in mice has been found to be linked to a new restriction-fragment length polymorphism (RFLP). Only C57BL/6 and closely related inbred strains displayed a 7.6-kb HindIII restriction fragment, while all other inbred strains tested displayed an 11.2-kb HindIII restriction fragment when using plasmid pRC2.3 as the hybridization probe. Polymorphisms in this region can also be detected with two other restriction enzymes: SacI and EcoRV. Linkage of Ah and the restriction-fragment length polymorphism was first detected using the BXD (C57BL/6 x DBA/2) recombinant inbred strains and was confirmed by a backcross. Both the restriction-fragment length polymorphism and Ah were not linked to the standard genetic markers Hba, Hbb, b, d, C-3, and W. However, comparison of the RFLP strain distribution pattern in the BXD recombinant inbred set with the strain distribution pattern of another RFLP, known to be located on chromosome 12, shows complete concordance in 24 of 24 strains, thereby locating Ah on chromosome 12.