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

(a) Transgenic animals can be used for the production biological products which are otherwise expensive to make. For example Rosie the transgenic cow produced human protein enriched milk. The milk contained human alpha-lactalbumin and thus was nutritionally more balanced for human babies than natural cow milk.
(b)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. Toxicity testing in such animals will allow us to obtain results in less time.