For chemical safety testing (toxicity testing), transgenic animals are made that carry genes which make them:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → more sensitive to toxic substances than non-transgenic animals
Transgenic animals carry a foreign gene. The book lists several uses: models of human diseases, biological products, vaccine safety testing and chemical safety (toxicity) testing. For toxicity testing, the animals are given genes that make them more sensitive to toxic substances than normal animals.
Option (1) serve as models for human diseases such as cancer and Alzheimer’s — Incorrect. Transgenic animals used as models of human diseases help in finding new treatments for diseases such as cancer and Alzheimer’s. That is a different use, not chemical safety testing.
Option (2) more sensitive to toxic substances than non-transgenic animals — Correct. For toxicity testing, the animals carry genes that make them more sensitive to toxic substances, so harmful effects show up quickly.
Option (3) produce the human protein α-1-antitrypsin used to treat emphysema — Incorrect. Transgenic animals that make human α-1-antitrypsin are used to produce a useful biological product (to treat emphysema). That is the ‘biological products’ use.
Option (4) suitable for testing the safety of the polio vaccine — Incorrect. Transgenic mice are used to test the safety of the polio vaccine. That is the ‘vaccine safety’ use, not chemical safety testing.
NCERT Extract:
Transgenic Animals – “… (iv) Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. … (v) Chemical safety testing: This is known as toxicity/safety testing. The procedure is the same as that used for testing toxicity of drugs. 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.”