Transgenic animals had a foreign gene intentionally inserted into their genome. These kinds of animals are most commonly created by the microinjection of DNA into the fertilized egg. This fertilized egg is subsequently implanted into the oviduct of a pseudopregnant surrogate mother. So the best process is microinjection for transgenic animals. The use of microinjection as a biological procedure began in the early 1990s, although even through the 1970s it was not used commonly. By the 1990s, its use had grown rapidly significantly and it is now considered a common laboratory technique.
Transgenic animals are used to identify the functions of specific factors in homeostatic systems through over- or under-expression of a modified gene. Transgenic animals are useful for disease models and producers of substances for human. Some transgenic animals are produced for specific economic feature. For example, transgenic cattle were created to produce milk containing particular for human proteins, which may help in the treatment of human body. Novel dual-reporter transgenic rodents (a gnawing mammal of an order that includes rats, mice, squirrels, hamsters, porcupines, and their relatives) enable cell tracking in animal models of stem cell transplantation. Establishment of dual reporter transgenic mice and rats, which express luciferase and GFP in all organs. Both luciferase and GFP signals were detected by in vivo imaging using their respective antibodies. Isolated mesenchymal stem cells from transgenic rodents showed both luciferase and GFP signals. Implantation of transgenic mesenchymal stem cells enables cell tracking in vivo.
Pros and cons of microinjection for transgenic animals:
Pros:
1) The genetically-engineered mouse carries a gene that promotes the development of human cancer so it can be studied more effectively.
2) Scientists also claim that these animals can be used in xenotransplantation.
3) Proponents of transgenic animals claim that this is important for people who require insulin treatment.
Cons:
1) According to opponents of transgenic animals, it is against moral ethics.
2) Due to the failure of some experiments, critics claim that products that come from transgenic animals are unsafe for human consumption.
3) The use of microinjection for transgenic animals is not a cheap process.