Evolution of mammalian carbonic anhydrase loci by tanden duplication: close linkage of Car-1 and Car-2 to the centromere region of chromosome 3 of the mouse.

Electrophoretic variants of two carbonic anhydrase enzymes CAR-1 (CA I) and Car-2 (CA II), have been found in the laboratory mouse, Mus musculus. These two loci are closely linked to each other and are located on chromosome 3 near its centromere. The close linkage of Car-1 and Car-2 supports the hypothesis that the present-day carbonic anhydrase loci are the result of tandem duplication of an earlier carbonic anhydrase locus with subsequent divergence. The red blood cells of mice of the subspecies M.m. casteneus have significantly reduced levels of CAR-1 and CAR-2.