Although there are many ethical issues surrounding transgenic animals this article is only concerning itself with some of the applications of the technology.
In medical science they are helping to expand our knowledge of the role genes play in the development of diseases and to test the safety and efficacy of new drugs.
a) Normal physiology and development
Transgenic animals can be used to study how genes are regulated, and how they affect the normal functions of the body and its development. This research includes the study of complex factors involved in the regulation of normal physiology and growth such as insulin-like growth factor (IGF). By introducing genes from other species that alter the formation of these proteins and studying the biological effects that result, more information can be gleaned about the role IGFs play in the body.
b) Study of disease
Many transgenic animals are used to increase our understanding of how genes contribute to the development of disease. The animals are genetically engineered to produce the disease symptoms so new and effective treatments can be studied. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s disease.
Some transgenic animals are produced to create specific products. This is for economic reasons as it's believed that far greater quantities of a product can be made at a much cheaper cost. Cows have been created to produce milk that contains particular human proteins to be used to treat emphysema. Similar attempts have made for treatment of phenylketonuria (PKU) and cystic fibrosis. In 1997, the first transgenic cow, Rosie, produced human protein enriched milk (2.4 grams per litre). The milk contained the human protein alpha lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk.
d) Vaccine safety
Transgenic mice can be used for testing the safety of vaccines before they are used on humans. One day they might completely replace the use of monkeys to test the safety of batches of polio vaccine.