Association With The SNPs At The Exons In β-LG B~* Gene And Production Traits And Protein Structure In Chinese Holstein

β-LG as a particular whey protein in fresh milk (7-12%) is secreted by mammary gland epithelium in wide variety of species such as cattle and other ruminants, but not found in human and rodent milk, and the function of the whey protein is not clearly. Up to now, several genetic variants were detected and affected the composition, quality and milk yield. Single nucleotide polymorphism (SNP) describes a single-base difference (transition, transversion mutation, insertion and deletion) in DNA sequences among individuals, and SNPs analysis are extensively applied in genetic studies of human diseases, breeding animals and plants. In order to investigate the association between the polymorphisms of theβ-LG variant B precursor gene (β-LG B*, GeneBank accession No: DQ489319) and milk production.β-LG B* gene, as a candidate and biochemical markers gene, was used for meliorating the heredity diathesis of the herd and enhancing the milk production. Polymerase chain reaction-Single strand conformation polymorphism (PCR-SSCP) analysis was adopted to analyze the polymorphism at the exon regions inβ-LG B* gene in Chinese Holstein. It was found that exon 1, 4 and 7 had polymorphisms, and SSCP band patterns were in Hardy-Weinberg equilibrium (P>0.05) in exon 1, not in Hardy-Weinberg equilibrium (P<0.01) in exon 4 and 7. In total, 41 SNPs were detected in this study: 2 SNPs located in exon 1, 4 SNPs in exon 4 and 35 SNPs in exon 7. The polymorphism information contents (PIC) of the SNPs were in median polymorphism (0.25 < PIC < 0.5) or other locus'PIC (PIC > 0.5) were in high polymorphism, excepted the loci (E4-4, PIC= 0.1867< 0.25) was in low polymorphism. In the statistical and linkage analysis results, it was suggested that 13 SNPs (E1-1, E1-2, E4-1, E4-2, E4-3, E4-4, E7-4, E7-20, E7-22, E7-23, E7-25, E7-26 and E7-31) might be associated with 305 products and total milk protein. 4 SNPs detected in exon 4 caused the amino acid sequences changed; and by analysis of the protein's homology models and prediction of the dimensional structure, which was also found that these SNPs induced the secondary and three-dimensional structures changed, and the changes might affect the stability of the protein. According to dairy herd improvement (DHI) and the data we analyzed, we obtained that the basis linkage informations between the SNPs in all exon regions of theβ-LG B* gene and milk traits or dimensional structure. Taken together, the SNPs at the exon regions of theβ-LG B* gene were remarkably associated with milk performance traits (milk protein and yield), and the data could to provide the genetics for the genetic breeding of the Chinese Holstein.