Fuente: WIPO "milk" This mammary specific recombinant DNA sequence encodes for bovine α-lactalbumin and promotes quantitative differences in gene expression among non-human mammals, the sequence being characterised by variations in the gene structure in the control region of bovine α-lactalbumin. An expression vector, expression systems and animals incorporating the above sequence are further features of the invention as is semen or milk produced by the animal and methods for identifying superior milk producing animals.