As it goes without saying that biotechnology largely deals with the manipulation of the genes (through genetic engineering). Different useful products have been made through this effective and researched manipulation. One such product of genetic engineering is that of transgenic animals. The word transgenic actually means genes from another species or foreign genes. Thus, transgenic animals are those animals whose genome has been modified by the insertion of foreign genes. This is brought about by applying methods of Genetic Engineering, like Recombinant DNA Technology and thus producing the desired characteristics by the introduction of those desired genes in a living organism.
For simplicity and to better understand how DNA is modified, we take the example of bacteria used to synthesize human insulin. First, mRNA is isolated from human insulin producing cells (Beta cells). This mRNA is then incubated with DNA free nucleotides and the enzyme reverse transcriptase, which is obtained from viruses, to form DNA from RNA. The DNA thus formed is single stranded and is called complementary DNA or cDNA. To this cDNA an additional strand of DNA is added that does not code for anything. This is done so that later it can be cut at specific sites using restriction enzymes. "Cutting" the cDNA gene using restriction enzymes produces "sticky ends". Specific restriction enzymes cut at specific sites.
This single stranded cDNA gene is then made double stranded using the enzyme DNA polymerase, and the DNA thus formed is cloned using Polymerase Chain Reaction (PCR). In order to insert the gene into a plasmid, which is the genetic material of the bacteria, it is cut open using the same restriction enzyme. This produces sticky ends complimentary to those of cDNA, which then "stick" together. Thus, cDNA is incorporated into the plasmid and the new modified genome of the bacteria is called Recombinant DNA. The recombinant DNA is transferred to bacterial cells, which then start producing insulin.
Transgenic animals serve many useful purposes in agriculture, medicine and research. They can be used to study various diseases and their treatments. For example, mice are naturally immune to polio because they do not possess cell surface receptors for the polio virus that humans do. Therefore, their genome is modified to give them the required cell surface receptors, and the mice are deliberately infected with polio virus. The diseased mice are then used for research on polio and its treatment. Similar methods are used in the study of different cancers and other diseases.
Transgenic animals are also used in the study of genetics to understand various traits of heredity and gene expression. This is reminiscent of Mendel's experiments; however, modern technology has made the process more precise and less tedious.
Selective breeding has been in use since ages in agriculture to increase the yield of milk, meat and even wool. Here again, transgenic animals have made things easier for farmers. Moreover, apart from just increasing the output of profitable products, transgenic animals can have their genome modified in order to be of nutritional benefit to humans. For example, human genes can be incorporated into cattle to produce milk and meat containing human proteins. Likewise, DNA of chickens can be modified to produce eggs with human proteins and less cholesterol content.
Furthermore, progress is being made in making xenotransplantation more successful.
Xenotransplantation is the transplantation of an organ from one organism to another; usually humans are at the receiving end. In fact, it is just a matter of time when most of the donor organs will be coming from transgenic animals, and recipients would be free from heavy immunosuppressive medication and the complications that accompany it. This is because scientists are working on creating transgenic animals that would have organs similar to humans in their cell surface proteins and hence would overcome the problem of graft rejection.
Thus, it can be stated and concluded fairly and confidently that over the period of time, it has been proven that these transgenic animals are quite beneficial for humans and seem to promise solutions to quite a lot of problems. Very hopefully, in near future there are going to be new vistas of success opened by these transgenic animals. Their help in research can unlock many answers and provide cures that we have long been waiting for.
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