(a) Transgenic animals
Animals that have had their DNA manipulated to possess and express an extra (foreign) gene so as to alter their DNA are known as Transgenic Animals.
(b) The transgenic animal having the largest number amongst all the existing transgenic animals is mice. They are 95% of all the existing transgenic animals.
(c) Purposes for which these animals are produced
a. Normal physiology and development – They are used to study how the process of development is regulated by the genes, how genes effect on the normal functioning of the body and its development. By introducing genes from other species that alter a specific factor and studying the biological effects that result, information is obtained about the biological role of the factor in the body.
b. Study of disease – They are used to study how genes contribute to development of diseases. Today they serve as models for many human diseases like cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer’s, Parkinson' disease etc.
c. 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 used to treat emphysema. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk.
d. Vaccine safety – They are used to test the safety of particular newly developed vaccine before the vaccine is given to human. At present they are tested on transgenic monkeys, but transgenic mice have shown promising results in this area and would replace the vaccine testing on monkeys in the years to come.
e. Chemical safety testing – is also known as toxicity / safety testing. In this the transgenic animals are made such that they are more sensitive to toxic substance. Then they are exposed to toxic substances and the resulting effects are studied. The procedure is the same as that used for testing toxicity of drugs. This method helps us to obtain desired results in much less time.
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