Molecular genetic markers of economically important traits in dairy cattle

The selection efficiency of complex quantitative economically important traits in dairy cattle depends on the identification of candidate genes responsible for these traits, as well as the determination of causative DNA polymorphism in these genes. Here, we review examples of DNA polymorphisms in coding and noncoding parts of genes that are associated with milk yield, milk fat and protein yields, milk fat and protein percentages, the biochemical composition of milk, and other milk production traits. Together with data of foreign authors, which were obtained predominantly for Holstein cattle, much attention in the review is paid to studies on Russian cattle breeds. Particular attention is dedicated to DNA polymorphisms in the genes encoding transcription factors, which can potentially affect a large number of traits. The results of association analyses are summarized in a table, and they present the progress of research in this area in recent years. Our analysis indicates that the majority of SNPs, which are associated with significant effects on milk production traits, are probably in a linkage disequilibrium with yet unknown mutations. The identification of functionally significant DNA polymorphisms and other genetic factors (epimutations, CNV) is necessary for effective marker-assisted selection and genomic selection of dairy cattle breeds.