The study of MHC-DRB3 gene Exon region polymorphisms by PCR-RFLP in some breeds of horses in Iran

The major histocompatibility complex (MHC) genes are very important in horse breeding according to relationship with immunity response and resistance or susceptibility to disease. The aim of this research is study of polymorphism possible in exon gene region and population genetics. To do this, 120 horses were selected randomly from Thoroughbred, Oldenburg, Caspian pony and Arab breeds. Genomic DNA was extracted via blood samples and polymerase chain reaction was done for a 309 bp MHC gene region. The PCR products were digested by RsaI restriction endonuclease for genotyping determination. Results show that there were three allele of A, B and C and six types of genotype of AA, AB, AC, BB, BC and CC with 0.3208, 0.3208 and 0.3584 allele frequency and 0.05, 0.25, 0.2917, 0.1333, 0.125 and 0.15 genotype frequency in all studied samples respectively. The most and least allele frequency in Thoroughbred, Oldenburg, Caspian pony and Arab are related to B, A, A, C and A, B, B, A alleles respectively. The Hardy-Weinberg equilibrium study by X2 and G2 tests shows the equilibrium situation in Oldenburg and Caspian pony breeds and non-equilibrium situation in Thoroughbred and Arab breeds. The overall results shows that the genetic diversity in studied samples can be used as a resource for horse breeding programs.