GENETIC-ENGINEERING OF MILK-COMPOSITION - MODIFICATION OF MILK COMPONENTS IN LACTATING TRANSGENIC ANIMALS

Recent progress in recombinant DNA technology as well as in embryo man ipulation and transfer has made the introduction of specific genes int o the germline of animals relatively commonplace. With appropriate gen etic constructs expression of the inserted genes in transgenic animals can be controlled in a tissue-specific and in a differentiation-speci fic manner; thus, it is now possible to consider alteration of the com position of milk produced by a lactating animal in any of a variety of ways. There is a growing list of foreign milk proteins that have been expressed, and one can envisage placing almost any protein gene of in terest under the control of the cis-acting promoter and enhancer eleme nts of a milk protein gene. Modification of milk composition can be ex tended not only to the proteins of commodity value but also, by manipu lation of key metabolic enzymes, to fat, lactose, and other minerals i n milk.