Culture of animal cells, on a large scale is more difficult and expensive than plant cells, the bacteria, yeast, etc. This is why the commercialization of natural products of animal origin is limited. However, most of the animal products have been produced by using bacteria as biological tool.
In India, Dr. K. Chandrashekharan, Center for Cellular and Molecular Biology (CCMB), Hyderabad emphasized the use of recombinant DNA technology for the introduction of foreign DNA into mammalian cells. This would help in curing certain genetic defects. Some of the examples of gene cloning in animals are described in Genetic Engineering for Human Welfare