Dairy Foods: Extended Shelf Life of Fluid Milk

This and earlier studies indicated that the casein genes are located in a mammalian specific genomic domain. This domain contains besides the casein genes a number of non-casein genes that share evolutionary ancestry, spatial expression patterns (mammary and salivary gland), and functional properties (secreted (phospho)-proteins, involvement in mineral homeostasis, and immune modulation). The presence and structure of orthologous genes in the mammalian species studied was determined. Predicted transcripts were cloned from a number of species. Phylogenetic analyses showed that the divergence of the casein genes is not only due to a high rate of nucleotide substitutions but also to the differential use of exons. Genomic rearrangements were identified that result in deletions of genomic segments containing casein genes, e.g. lack of alpha-s2-like genes in shrew. Overall there is remarkable conservation in this region with regard to the genes present, gene structure, and gene order and orientation despite high divergence at the nucleotide level.