Genetic Variability of Alpha-Casein, Beta-Casein, and Kappa-Casein Genes in Holstein-Friesian, Simmental and Brown Swiss Cattle

Abstract

This study aims to determine the genotypes and allele frequencies of polymorphisms of bovine alpha S1-ca-sein (CSN1S1), alpha S2-casein (CSN1S2), /3-casein (CSN2) and kappa-casein (CSN3) genes in Holstein-Friesian, Simmental, and Brown Swiss breeds. DNA was isolated from milk samples and gene regions were amplified using optimized PCR protocols. Sanger sequencing was performed to genotyping PCR products. CSN1S1 and CSN1S2 genes in three cattle breeds were observed to be monomorphic. Three different genotypes were observed for the CSN2 gene in Holstein-Friesian and two genotypes in Brown Swiss, while the Simmental breed was monomorphic. For the CSN3 gene was observed three different genotypes in Holstein-Friesian and Brown Swiss, two different genotypes in Simmental. Also, a novel single nucleotide polymorphism (SNP) was identified in the sequence region in the CSN2 gene exon 7 of three cattle breeds in this study. This SNP, c.249C>G, were non-synonymous, which leads to the change of p.N68K in amino acid residue of bovine /3-casein. This SNP is thought to be detected for the first time in Bos taurus genus. However, it was concluded that it would be appropriate to carry out more studies on this new SNP point in larger populations.