$\left(a\right)$ Why are transgenic animals being produced?
$\left(b\right)$ How can man benefit from the modifications introduced in transgenic animals?

Introduction to transgenic animals :
The animals whose genome has been modified to carry and express a foreign gene (gene of other organisms) are called transgenic animals. Examples include transgenic mice, rats, pigs, cows etc. that have been modified to carry a transgene.

Reason of production of transgenic animals :
Transgenic animals are being produced for various purposes:

• For research purposes such as to study the effect of a drug, its toxicity and side effects and to evaluate the efficacy of vaccines.
• To produce a better yield of products obtained from animals as well as their nutritional enrichment such as milk.
• To produce good quality breeds.
• To develop a disease model and study the mechanism and prognosis of a disease.

Biological products:

• Good quality milk with increased albumin content. Rosie, the cow has produced milk containing more amounts of human alpha-lactalbumin that has higher nutritional value.
• Transgenic cattle are produced in a way that they express a particular protein that can be used for treatment of diseases, such as alpha-1 antitrypsin is expressed in cattle to treat emphysema.

Studying diseases:
Transgenic mice are widely used as disease models of diseases such as cystic fibrosis, Alzheimer’s diseases, cancer etc. to have a better understanding about the diseases and their prognosis.

Drug safety testing:
Transgenic animals are also used to study the effect and safety of a drug before making it commercially available.

Vaccine safety :
To check the efficacy, side-effects and safety of a vaccine, it is tested on transgenic animals or disease models before being introduced in human trials.

Basic understanding of normal physiology and development :
Transgenic animals such as transgenic mice are used to study the function of genes, their regulation. This is because mice share a lot of gene similarity with humans.