Genetically modified animal models also called as transgenic animals represent a promising tool in biology to understand the host pathogen interactions and gene function in the purview of disease susceptibility and its progression. Apart from many animal models mice represent one of the best tools to understand many of the above important roles in the discovery and development of new disease treatments.

9.1 Types of Transgenic Animals

Transgenic animals are genetically altered with specific characteristics which otherwise would not be present in that specific animal. In general, transgenic animals have either DNA added (to express an additional gene) or have their genome altered (to abolish or modify the expression of an existing gene). Rodents particularly mice comprise of over 95% of transgenic animals used in biomedical research. The mouse is the model organism of choice because of the following reasons:

• •  Complete mice genome sequence is available.

•  Easy genetic manipulation of mice cells and embryos.

•  Short gestation period and large litter size.

•  Availability of major antibodies and other molecular biology tools.

•  Possibility to perform physiologic and behavioral tests that can be directly linked to human disease.

Other transgenic species include cattle, pig, sheep and rats. Their use in pharmaceutical research has so far been limited due to technical constraints. Recent advances in molecular biology techniques may allow us to use transgenic rat for the development of many human therapeutics where the rat is a better model than the mouse.