Animal Genetics zyxwvutsrq 1992,23, zyxwvutsr 143-150 Genetic polymorphism and close linkage of two plasma protein loci in dogs R. K. JUNEJA zyxwvut & T. SHIBATA* Department of Animal Breeding and Genetics, Swedish University zyx of Agricultural Sciences, Uppsala, Sweden Summary. By using a simple method of two-dimensional horizontal electrophoresis, phenotypes of an unidentified plasma protein (PA4) were determined in 967 dogs belonging to 43 different breeds. Two codominant, autosomal alleles zyx (F and zy S) of PA4 were reported. While many of the breeds of middle and north-eastern Asia (akita inu, Alaskan malamute, chow chow, samoyed, Siberian husky and Tibetan terrier) showed a substantial frequency (0.1 to 0-6) of the S allele, a majority of the European breeds had only the F allele. Evidence was provided that the PA4 locus is closely linked to the plasma pretransferrin 1 locus (PRTI). No recombinant was observed in 45 informative offspring studied. In nearly all breeds, the PA4 S allele was almost always in coupling phase with the PRTl F allele. Keywords: dog, breeds, plasma proteins, genetic polymorphism, linkage, gene frequency, gel elec- trophoresis Introduction Genetic polymorphism of about 15 different plasma proteins in dogs has previously been reported (for references see Juneja et al. 1987, 1989). Seven of these polymorphisms were described by using a simple method of two-dimensional electrophoresis followed by protein staining. These proteins are al-protease inhibitor (PIl), alB-glycoprotein (AlBG), apolipoprotein A4 (APOA4) and four unidentified ones - postalbumin 1 and 3 (PA1 and PA3) and pretransferrin 1 and 2 (PRT1 and PRT2). All of these except PRT2 showed a high degree of polymorphism in the common European breeds. PA3 was not seen in fresh plasma samples but was clearly observed in plasma stored at -20°C for more than 2 years (Juneja et al. 1987, 1989). By using the same method, we describe here genetic polymorphism of an additional, unidentified plasma protein called postalbumin zyx 4 (PA4). We provide evidence for close linkage between the PA4 and PRTl loci. The distributions of PA4, PRTl haplotypes in different breeds are reported. * On leave from Department of Animal Science, Kyushu Tokai University, Kuamoto, Japan. Correspondence: Dr R.K. Juneja,Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 7023, S-750 07 Uppsala 7, Sweden. Accepted 31 May I991 143