World Library  
Flag as Inappropriate
Email this Article

Transgenic

 

Transgenic

Transgenesis is the process of introducing an exogenous gene – called a transgene – into a living organism so that the organism will exhibit a new property and transmit that property to its offspring. Transgenesis can be facilitated by liposomes, plasmid vectors, viral vectors, pronuclear injection, protoplast fusion, and ballistic DNA injection.

Transgenic organisms are able to express foreign genes because the genetic code is similar for all organisms. This means that a specific DNA sequence will code for the same protein in all organisms. Due to this similarity in protein sequence, scientists can cut DNA at these common protein points and add other genes. An example of this is the "super mice" of the 1980s. These mice were able to produce the human protein tPA to treat blood clots.

Using plasmids from bacteria

The most common type of transgenesis research is done with bacteria and viruses which are able to replicate foreign DNA.[1] The plasmid DNA is cut using restriction enzymes, while the DNA to be copied is also cut with the same restriction enzyme, producing sticky-ends. This allows the foreign DNA to hybridise with the plasmid DNA and be sealed by DNA ligase enzyme, creating a genetic code not normally found in nature. Altered DNA is inserted into Plasmid for replication.[2]

Gene Transfer Technology

1. DNA Microinjection- The Desired gene construct is injected in the pronucleus of a reproductive cell using a glass needle around 0.5 to 5 micrometers in diameter. The manipulated cell is cultured in vitro to develop to a specific embryonic phase, is then transferred to a recipient female. DNA microinjection does not have a high success rate (roughly 2% of all injected subjects), even if the new DNA is incorporated in the genome, if it is not accepted by the germ-line the new traits will not appear in their offspring. If DNA is injected in multiple sites the chances of over-expression increase.[3]

2. Retrovirus-mediated gene Transfer- A retrovirus is a virus that carries its genetic material in the form of RNA rather than DNA. Retroviruses are used as vectors to transfer genetic material into the host cell. The result is a chimera, an organism consisting of tissues or parts of diverse genetic constitution. Chimeras are inbred for as many as 20 generations until homozygous genetic offspring are born.[4]

3. Embryonic cell-mediated gene Transfer- The manipulated gene construct is inserted into totipotent stem cells, cells which can develop into any specialized cell. Cells containing the desired DNA are incorporated into the host’s embryo, resulting in a chimeric animal. Unlike the other two methods of injection which require live transgenic offspring for testing, embryonic cell transfer can be tested at the cell stage.

Pharming

Pharming is a portmanteau of "farming" and "pharmaceutical" and refers to the use of genetic engineering to insert genes that code for useful pharmaceuticals into host animals or plants that would otherwise not express those genes, thus creating a genetically modified organism (GMO).[5] Pharming has gained application in biotechnology since the development of trangsgenic "super mice" in 1982. "Super mice" were genetically altered to produce the human drug, tPA (tissue plasminogen activator to treat blood clots), in 1987.[6] Since the "super mice" pharming has come a long way. Using RNA interference scientists have produced a cow whose milk contains increased amounts of casein, a protein used to make cheese and other foods, and almost no beta-lactoglobulin, a component in milk whey protein that causes allergies.[7]

"Pharming Examples:"[8]

  • Haemoglobin as a blood substitute
  • human protein C anticoagulant
  • alpha-1 antitrypsin (AAT) for treatment of AAT deficiency
  • insulin for diabetes treatment
  • vaccines (antigens)
  • growth hormones for treatment of deficiencies
  • factor VIII blood clotting factor
  • factor IX blood clotting factor
  • fibrinogen blood clotting factor
  • lactoferrin as an infant formula additive

See also

References

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.