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.