Sequences polymorphism and variation of major histocompatibility complex DRB exon 2 of black Dahe pig

Abstract

DNA sequences of swine leukocyte antigens (SLA) DRB exon 2 from five populations were used to investigate
genetic polymorphism of black Dahe pig in Yunnan province of China. Our results showed that the SLA-DRB
exon 2 of black Dahe pig obtained high variable rate of 23.50%, which was higher than the values analyzed for
cattles or other livestocks. The average G + C content at the third synonymous variable coding positions (GC3)
was closed to 0.78. The amino acids composition rate and majority of relative synonymous codon usage were
near the ranges of 0.00 to 11.27 and 1.00 to 2.00, respectively. These significant polymorphism, high GC3
content and differentiation of preferred codon usage could be resulted from over dominance selection, base
compositional bias and the diversity of gene expression level. Aforementioned results adequately testified the
SLA-DRB exon 2 may be an important genetic marker for studies in genetic diversity, population genetics,
breeding reproduction investigation and exploring new functional genes of black Dahe pig.