Which of the following is not a benefit of transgenic animals to man?

The correct answer is Option (2) → Early detection of diseases.

Transgenic animals are produced for several reasons: to study normal physiology and development, to study diseases and test new treatments, to make biological products, and to test the safety of vaccines and chemicals. Early detection of a disease in a patient is done by molecular diagnosis (rDNA technology, PCR, ELISA), not by transgenic animals.

Option (1) Investigation of new treatments for diseases. — A benefit of transgenic animals. Transgenic animals are made as models for human diseases such as cancer, so that new treatments can be investigated.

Option (2) Early detection of diseases. — Not a benefit of transgenic animals. Early detection of disease comes from techniques of molecular diagnosis such as PCR and ELISA.

Option (3) Testing the safety of vaccines. — A benefit of transgenic animals. Transgenic mice are used to test the safety of vaccines, such as the polio vaccine, before they are used on humans.

Option (4) To produce useful biological products. — A benefit of transgenic animals. They can produce useful biological products, such as the human protein α-1-antitrypsin.

NCERT Extract:
Transgenic Animals – “… (ii) Study of disease: Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease. These are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. … (iv) Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans.”
Molecular Diagnosis – “… Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.”