December 28, 2013

Transgenic Animals - Methods of Transgensis , Applications of Transgenic Animals.

What   are   transgenic  animals?  What   are   the   methods  of transgensis ?
Animals that have their DNA manipulated to possess and express on extra (foreign) gene are known as transgenic animals. Transgenic rats, rabbits, pigs, cows and fish have been produced although over 95% of all existing transgenic animals are mice. In  creating  a  transgenic  animal,  the  transgene should be introduced  just  after  fertilization  into  the  male  pro-nucleus known as ‘transgensis’.
There are 3 methods of transgensis.
1. Micro –Injection
2. Nuclear Transplant
3. Trans-embryo technology.
1. Micro-Injection: It involves introduction of trans-gene into the male pro-nucleus of the zygote just after fertilization, by a microscopic needle. The probability of gensis is 10%.
2. Nuclear transplant: This method involves introducing a transgene into a separate nucleus and then transplanting it into a e-nucleated egg. The probability of transgensis is 2.5%.
3. Trans-embryo technology: This method involves the use of lenti-virus to insert transgene into the male pro-nucleus.  Viruses  that  integrate  their  genetic  material  with  host  cell genome are known as ‘lenti viruses. 100 % gensis is possible by this method. The most widely used technique to produce transgenic organisms is micro-injection since it is very easy to carry out.
Some of the benefits from such modifications are:

1.  Normal physiology and development: Transgenic animals can be specifically designed to allow the study of how genes are regulated and how they affect the normal functions of the body and its development. E.g. study of complex factors involved in growth such as insulin like factor. By introducing genes from other species that alter the formation of this factor and studying the biological effects that result information is obtained about the biological role of the factor in the body.

2.Study of disease: Many transgenic animals are designed to increase our understanding of hoe gees contribute to the development of disease. They are specifically made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.

3. Biological products: Medicines required to treat certain human diseases can contain biological products, but such products are often expensive to make. Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA( or genes) which codes for a particular product such as human protein(   -1- antitrypsin) used to treat emphysema. Similarly attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk(2.4 gma/litre). The milk contained the human alpha- lactalbumin and was nutritionally a  more balanced product for human babies than natural cow milk.

4. Vaccine Safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are used to test the safety of the polio vaccine. If successful and fund to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine.

5. Chemical safety Testing: Transgenic animals are made that carry genes which make them more sensitive to toxic substances than non transgenic animals. They are then exposed to the toxic substances and the effects studied. Toxicity testing in such animals will allow us to obtain results in less time.


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