Match the List-I with List-II LIST I — Nature of substances LIST II — Effect…

Concept: toxicology names a hazardous substance after the biological target its effect acts upon, and each of these four terms is built from a root that names that target — allergy (immune hypersensitivity), carcinoma (cancer), mutation (a change in DNA), and the Greek teratos (a malformed birth). So an allergen provokes an immune response, a carcinogen initiates cancer, a mutagen alters genetic material, and a teratogen disturbs the development of an embryo or fetus.

Application: applying each definition to the four entries of List-I assigns exactly one effect from List-II to each.

Cross-check: the pairs most often confused separate cleanly on the endpoint each term is defined by.

• Mutagen versus carcinogen: a mutagen is defined by the damage it does to DNA, whereas a carcinogen is defined by the tumour that follows. Many carcinogens do act through mutation, but the defining evidence differs — a measured genetic change for one, an increased cancer incidence for the other.

• Teratogen versus mutagen: thalidomide caused severe limb malformation in fetuses without acting as a mutagen, which shows that harm to development during gestation is a separate endpoint from damage to genetic material.

• Allergen: of the four, only an allergen works by switching the immune system on — an IgE-mediated hypersensitivity reaction — rather than by injuring cells, DNA or the developing embryo.

Result: the matching that follows from these definitions is A-III, B-I, C-IV, D-II — allergens with immune activation, carcinogens with cancer, mutagens with damage to genetic material, and teratogens with impaired embryonic growth.