NCERT · Class 12 · Biology · Biotechnology and its ApplicationsWhat are transgenic animals? Give one example of a transgenic animal and state its main application.

Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals. Transgenic rats, rabbits, pigs, sheep, cows, and fish have been produced, although over 95 percent of all existing transgenic animals are mice. \nOne prominent example of a transgenic animal is 'Rosie', the first transgenic cow produced in 1997. Rosie produced human protein-enriched milk. Her milk contained the human alpha-lactalbumin, which was nutritionally more balanced for human babies than natural cow milk. \nThe main applications of transgenic animals include:

1. Study of normal physiology and development: Transgenic animals can be specifically designed to allow us to study how genes are regulated and how they affect the normal functions of the body and its development.
2. Study of diseases: Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease. These are specially made as models for human diseases such as cancer, cystic fibrosis, rheumatoid arthritis, and Alzheimer's.
3. Biological products: 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 (alpha-1-antitrypsin) used to treat emphysema.
4. Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Polio vaccine was safety-tested in transgenic mice before being used on humans.
5. Chemical safety testing: This is known as toxicity/safety testing. Transgenic animals are made that carry genes which make them more sensitive to toxic substances than non-transgenic animals. Toxicity testing in such animals will allow us to obtain results in less time.