Abstract: Foreign gene (double stranded DNA) is maybe integrated in different DNA strand of the same chromosome as an exon The first generation of transgenic fish is mosaic. The homozygote generation of transgenic fish is maybe obtained by the three-cross depuration process. The heterozygote generation with single heterozygosis is obtained by twice backcross mating between mosaic and pure individual. Finally, the homozygote generation is obtained by self-cross mating of the second heterozygote.