Polymorphism of mannose-6-phosphate isomerase in cattle

Enzymo-electrophoresis and enzymo-electrofocusing of white cells and of muscular extracts of cattle has revealed four kinds of phenotypic patterns. Evidence presented here indicates that three of these phenotypes are controlled by two codominant, autosomal alleles, MPI ^B and MPI ^C. The allele MPI ^C occurs with a frequency of about 0.10 in most of the breeds studied and of about 0.03 in the Charolais breed. The fourth, very rare, two-banded phenotype, encountered mostly in purebred and crossbred Charolais, is believed to be under the dependence of a third allele MPI ^A but the breeding tests are lacking.