Which of the following factors are studied with the help of transgenic animals?

All of these.

a- Study of complex factors involved in growth.

b- Study how genes contribute to the development of disease.

c- Transgenic mice are being used to test the safety of the polio vaccine.

d- All of these is the correct option .

Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine.

Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease.

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 complex factors involved in growth such as insulin-like growth factor.