Transferencia génica en pecesbases técnicasy aplicaciones

Laburpena

The application of recombinant DNA methodology to biotechnology hasresulted in significant progress in very different processes. Gene transfer inhigher eukaryotes is one of its main achievements. Gene transfer makes pos-sible the modification of hereditary traits in an animal. This can be achievedby introducing a new gene, or by replacing a specific gene of the genome (gene targeting). This second approach allows the generation of knock-out animals, and requires the availability of in vitro cultured totipotent cells. This method is little developed in fish, when compared to what has been accomplished in mouse. The most usual methodology in fish is the direct introduction of an exogenous gene in the fertilized egg. Different methods have been tested to introduce the DNA, but the more common one is cytoplasmic microinjection of the early cleavage embryo. One of the limiting steps in the generation of a transgenic fish is the integration of the foreign DNA in the host genome.This integration occurs at random and happens later during the development of the embryo, resulting in a mosaic adult organism with low incidence of the transgene in the germline.Most of the gene transfer work in fish is related with basic research anduses model species. Among the biotechnological applications using commer-cial fish species the biggest efforts have been directed to produce transgenicfish, mostly salmonids, with high growing rates, through the introductionof multiples copies of the growth hormone gene. Less developed approachesinclude: generation of transgenic fish aimed to resist freezing, enhancedprotection against pathogens, control of sexual maturation, or modificationof animal metabolism. Other kind of studies have focused in the productionof transgenic fish to monitor environmental contaminants or the use of theseanimals as biofactories.All this research has aroused a lot of interest, but it has also lead to theexistence of risks derived from its use. These include, environmental risksbased on a possible escape of the transgenic animals, and also doubts abouttheir suitability for human consumption, as well as ethic problems derivedfrom the manipulation of the genome