How have transgenic animals proved to be beneficial in :
(a) Production of biological products.
(b) chemical safety testing.

Explanation

(a) Transgenic animals : These animals have had their DNA manipulated to incorporate and express an extra gene. These have been useful for production of bioligical products such as production of human protein (alpha-1 antitrypsin) for treatment of emphysema.
Transgenic cow Rosie produced human alpha lactalbumin enriched milk (2.4 gms protein per liter) which was more balanced product for human babies than natural cow milk.
(b) Chemical safety testing : Transgenic animals are made more sensitive to toxic substance than non-transgenic animals by introduction of certain genes. These transgenic animals are then exposed to toxic substances under study. Toxicity testing in such animals takes less time.