Polymorphism of kappa-casein in Italian goat breeds: A new ACRS-PCR designed DNA test for discrimination of A and B Alleles

摘要

The objective of this study was to develop a DNA test for rapid characterisation of goat r-casein (kappa-CN) A and B variants and to study this polymorphism in Italian goat breeds. Genetic polymorphism of kappa-CN gene was, in addition to isoelectric focusing, analysed according to a new technique designated as amplification created restriction site. Two alleles that differ in one nucleotide mutation (G circle divide A) in exon 4 were characterised. The 167-bp PCR product surrounding the nucleotide mutation was amplified from genomic DNA and the PCR product was digested with MaeIII. After digestion the A allele gives three fragments of 77, 65 and 25 bp in comparison with the B allele which gives two fragments of 90 and 77 bp. The analysis of allele frequency distribution at kappa-CN locus, based on 401 individual samples, revealed significant differences among three goat breeds from the north of Italy (Nera di Verzasca, Frontalasca and Alpine) with frequency of kappa-CN B allele around 0.3, versus two goat breeds from the south of Italy (Maltese and Sarda) with frequency of kappa-CN B allele around 0.5. While two goat breeds (Maltese and Nera di Verzasca) did not show significant deviations from the Hardy-Weinberg equilibrium, a highly significant excess of heterozygote genotype (AB) was observed in Alpine, Frontalasca and Sarda goats. Here the developed DNA method and observed relatively high frequency of kappa-CN B allele give a prerequisite for the assessment of research related to the simultaneous estimation of the effects of composite alpha(s1)/kappa-CN genotypes on milk production and cheese-making properties.