Gene transfers have been successful several fish, i.e. common carp, rainbow trout. Atlantic salmon, catfish, gold fish, loach, medaka, tilapia, zebra fish etc. The genes transferred into fish including salmon or rainbow trout growth hormone, chicken- δ – crystalline protein, winter flounder antifreeze protein, E Coli, β galaetosidase and E-coli hygromycin resistance gene.
Transfection is achieved either by micro injection of the DNA construct in to egg cytoplasm or by electro poration. Microinjection is performed within few hours after fertilization. Transfected ova arte cultured in water where they hatch.
The rate of survival of microinjected embryo varies from 35 to 80% of which 10-70% may be transgenic. Electro poration is much less tedious than microinjection and can be used to transfect a very large number of eggs within a limited period of time. About 20% or more of the embryos surviving electroporation give rise to transgenic fish.
Improved growth was sought to be achieved by transferring salmon or rainbow trout growth hormone (GH) gene in channel catfish, common corp, gold fish, loach, medaka, rainbow trout, salamon and tilapia. Transgenic families of a fish differ in the level of expression of GH as well their body growth; this is most likely the consequence of positional effects due to random integration of the transgene. Some transgenic families show up to 60% increase in body growth. A combination of family selection with mass selection among the transgenic individuals has yielded the fastest growing fish line. Generally the transgene is stably inherited.
In addition, many other genes have been successfully introduced and expressed in fish; these genes include antifreeze protein gene, hygromycin resistance gene, neomycin resistance gene, a-globin gene, β- galactosidase gene, chicken δ-crystalline protein gene, bacterial or insect luciferage gene. In most of the studies gene transfers were successful, the transgenes were expressed and inherited stably.