1. Normal physiology and development : Transgenic animals are specifically designed to allow studying about. 

• How the genes are regulated. 
• How the gene affects normal functioning of body. 
• How it affects growth and development. E.g. insulin like growth factor. The animals are made transgenic to know the biological effect and result. 

2. Study of disease : 

Transgenic animals are designed to understand how genes contribute to the development of disease like cancers, cystic fibrosis, rheumatoid arthritis and Alzheimer’s. 

3. Biological products : 

Transgenic animals are used to produce biological product of human interest : 

• ∞ -1 antitrypsin used to treat emphysema. 
• Proteins for treatment for PKU and cystic fibrosis. 
• Transgenic cow Rosie, produce human protein enriched milk (2.4 gm / lit. human a – lactalbumin). 

4. Vaccine safety 

• Transgenic mice are being developed and use in testing the safety of vaccines before they are used for humans. 
• Polio vaccine is tested in mice. 
• Chemical safety testing 
• This is also known as tocicity / safety testing. 
• Transgenic animals are used to know the effects of toxic chemicals.