Explanation

Animals whose DNA is manipulated to process and express an extra (Foreign) gene are known as transgenic animals. Following are the common reasons for developing transgenic animals (i) Study of normal physiology and development $e.g.,$ study of complex growth factors like insulin like growth factor (ii) Study of disease Transgenic model have been developed for many human diseases like cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s disease (iii) Obtain useful biological products, $e.g.,$ human protein $(\alpha$-1-antitrypsin) is used to treat emphysema (iv) Vaccine safety-Transgenic mice are developed to test the safety of vaccine before being used on humans. For example polio vaccine (v) Chemical safety testing; Transgenic animals are made to carry genes, which makes them more sensitive to the toxic substances than non-transgenic animals