1. Transgenic animals are genetically modified animals that are used in a wide range of fields. 

2. In the field of medical research, transgenic animals like mice are used to identify the functions of specific factors through over- or under-expression of a modified gene (the inserted transgene). They are designed to study how genes contribute to the development of disease. These animals are used to investigate development of diseases like cancer, cystic fibrosis, rheumatoid arthritis, etc. 

3. In toxicology field, they are used for detection of toxicants. They are used as responsive test animals. Transgenic animals are used to evaluate a specific genetic change in molecular biology studies. 

4. In pharmaceutical industry, transgenic animals are used for targeted production of pharmaceutical proteins, drug production and product efficacy testing. 

5. They are also used in study of mammalian developmental genetics.

Transgenic farm animals like cattle, sheep, v poultry, pigs, etc. exhibit many desirable traits.

1. Improved quantity and quality of meat 

2. Improved quality and quantity of milk 

3. More egg production 

4. Better quality and quantity of wool 

5. Disease resistance 

6. Production of low-cost pharmaceuticals and biologicals