STRUCTURAL AND MOLECULAR-GENETIC CHARACTERISTICS OF THE CSN2 GENE IN CATTLE BREEDS: A REVIEW AND FUTURE PERSPECTIVES

This study investigates the structural and molecular-genetic characteristics of the CSN2 gene, which encodes β-casein-one of the key milk protein components in cattle. Located on chromosome 6 of the bovine genome, the CSN2 gene is a protein-coding sequence comprising nine exons, according to contemporary genomic annotation data. Nucleotide substitutions within the CSN2 gene drive the formation of diverse allelic variants that directly alter the amino acid composition of the β-casein protein. Notably, the A1 and A2 β-casein variants are distinguished by a single amino acid substitution at position 67. This genetic variability is of paramount importance for characterizing the genetic profiles of cattle breeds, evaluating milk protein composition, and identifying promising molecular markers for marker-assisted selection. Elucidating the structure and polymorphisms of the CSN2 gene represents a critical research direction, particularly for molecular-level characterization and conservation of the gene pool in local and genetically valuable cattle breeds.