Organism whose gene has been altered, by introduction of foregin genes into its genome. It is most frequently achieved by integration of cloned DNA sequences following their injection into the fertilized egg. This fertilized egg divides mitotically to form the whole organism so that all the cells of the organism will carry the transferred gene. The transferred genes are known as transgenes. Transgenic animals produced by this technology include mice, Drosophila, Xenopus and some of the fish species.