Abstract

Transgenesis  is  the  process  by which gene modication is achieved through  the  introduction  of  gene(s)  of interest into a cell or an animal embryo to develop transgenic cell lines or transgenic animals, respectively. A variety of methods such  as  lipofection,  electroporation, magnetofection,  sonoporation,  biolistic particle  delivery  and  viruses  have  been employed  to  introduce DNA  into  in  vitro cultured  cells.  Viral  ransfection  and microinjection are the two main methods used to introduce DNA into preimplantation embryos  to  generate  transgenic  animals. Transgenesis  occur  through  random integration  of  introduced  genes  into  the host genome. The advent of animal cloning allowed modication of donor broblasts to generate stable transgenic cells  in  vitro which can then be used to create transgenic animals  through  cloning  via  somatic  cell nuclear  transfer  (SCNT).  This  approach allows creating multiple clones that would express  the  same  phenotype,  thereby expanding  the  scope  of  creating  herds  of animals with the desired phenotype. While viral  and  the  microinjection  methods produced transgenic animals with random  integration,  recent  advances  in  gene targeting/editing technologies such as Zinc Finger  Nuclease  (ZFN),  Transcription Activator-like Effector Nuclease (TALEN) and  CRISPR/Cas9  promise  precise  gene targeting for better outcomes. The methods, and  pros  and  cons  of  various  approaches used to produce transgenic animals and the utility of transgenic animals are discussed in this review.

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