MGI:97564Four electrophoretic variants are known, each with a 5-band pattern: the a allele in C57BL/6, BALB/c and AKR; b allele in DBA/2 and SJL; c allele in C3H/He; and d allele in 129/Re. Heterozygotes show a mixture of bands. Mice homozygous for a spontaneous null allele or ENU induced alleles are viable.