Studies on Milk Protein Polymorphism in Danish Cattle and the Interaction of the Controlling Genes

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Abstract
In milk samples from 1520 heifers and 542 dams the αsl-, β- and x-casein types and the β-lactoglobulin components, A and B, were determined simultaneously by means of electrophoresis in thin starchurea-gels. The theory of inheritance advanced within each system from previous investigations was confirmed. Family data on the transmission of the two x-casein components A and B are given (Table 3). The frequencies of the controlling genes in Danish cattle were computed for each of the systems (Table 2). With traditional starch-gel-electrophoresis, four components, termed A, B, G and D, could be demonstrated in the β-lactoglobulin (Figs. 3 and 4). The four components are presumed to be controlled by four allele genes. The αsl-, β- and ϰ-casein phenotypes were not independently distributed and the segregation of casein types among offspring from bulls heterozygotic in two or three casein type-systems strongly suggests that the genetic variations of the αsl-, β- and ϰ-casein are controlled by genes at a single locus. Then, a minimum of 8 alleles may account for the phenotypes observed among 521 Danish cows (Table 6). Linkage of less than five per cent recombination could be excluded between the casein types and the β-lactoglobulin types.