Recently, the global demand for the production of A2 milk, a genotype of beta-casein, has increased, and due to its nutritional advantages and higher price, the selection process has changed in favor of this allele and its homozygous genotype. The purpose of this study was to investigate a precise method for detecting beta-casein genotypes in cattle. For this purpose, blood sampling was done from 72 Brown Swiss cows. After DNA extraction and quality check, a 251 nucleotide fragment of beta-casein gene was amplified by PCR reaction. The PCR product was digested by DdeI restriction enzyme and genotype was determined after agarose gel electrophoresis. The results showed that the frequency of A2 allele was 52.1% and the frequency of A2A2 genotype was 29% in the studied population. The method used in this research showed that the A2 allele of the beta-casein gene can be identified with a high accuracy and confidence.

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