Animals which contain and express in its genome one or more foreign genes are called transgenic animals. 

Men are benefited by making transgenic animals in following ways– 

(1) Knowledge of normal physiology and development – Transgenic animals can be specifically designed to allow the study of how genes are regulated and how they affect the normal functions of the body and its development. e.g. Study of effect of insulin on transgenic animals 

(2) Study of disease – Transgenic animals are specially made to serve as models for human disease so that investigation of new treatments for disease is made possible. Today transgenic models exist for many human diseases such as cancer, Alzheimer’s, etc. 

(3) Biological products – For example human protein –1 antitrypsin used to treat emphysema can be produced by transgenic animals. 

(4) Vaccine safety – Transgenic mice are being used in testing the safety of vaccines before they are used on humans eg. Polio vaccine. 

(5) Chemical safety testing – Transgenic animals are made that carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to the toxic substances and the effects studied.