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

Explanation

**Step-by-Step Solution:**

**Introduction to Transgenic Animals:**
Transgenic animals are those that have had a foreign gene deliberately inserted into their genome. This genetic modification allows them to express new traits or produce specific biological products that can be beneficial for various applications.

**(a) Production of Biological Products:**
1. **Example of Transgenic Animal:** One notable example of a transgenic animal is Rosie, a genetically modified cow.
2. **Gene Insertion:** Rosie was engineered to carry the human alpha-lactalbumin gene.
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