UPSC Prelims 2020— Question 17

This question tests pronuclear transfer and mitochondrial disease. The key concept is: Pronuclear transfer is a mitochondrial-replacement technique in which nuclear genetic material is transferred between fertilized eggs/embryos so that disease-causing mitochondrial DNA can be avoided. Its principal medical objective is prevention of transmission of serious mitochondrial disorders. The verified answer for the uploaded Set-B paper is option D. Option A — Fertilization of egg in vitro by the donor sperm: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Pronuclear transfer is a mitochondrial-replacement technique in which nuclear genetic material is transferred between fertilized eggs/embryos so that disease-causing mitochondrial DNA can be avoided. Its principal medical objective is prevention of transmission of serious mitochondrial disorders. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option B — Genetic modification of sperm-producing cells: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Pronuclear transfer is a mitochondrial-replacement technique in which nuclear genetic material is transferred between fertilized eggs/embryos so that disease-causing mitochondrial DNA can be avoided. Its principal medical objective is prevention of transmission of serious mitochondrial disorders. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option C — Development of stem cells into functional embryos: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Pronuclear transfer is a mitochondrial-replacement technique in which nuclear genetic material is transferred between fertilized eggs/embryos so that disease-causing mitochondrial DNA can be avoided. Its principal medical objective is prevention of transmission of serious mitochondrial disorders. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option D — Prevention of mitochondrial diseases in offspring: This is the correct option. It matches the verified conclusion because Pronuclear transfer is a mitochondrial-replacement technique in which nuclear genetic material is transferred between fertilized eggs/embryos so that disease-causing mitochondrial DNA can be avoided. Its principal medical objective is prevention of transmission of serious mitochondrial disorders. The wording of the option is consistent with the governing concept tested by the question. For UPSC-style elimination, first identify the exact proposition being tested, then evaluate each statement independently before comparing the answer codes. Avoid treating a broad or absolute statement as correct merely because its general theme is familiar. The precise qualifiers in the question—such as 'all', 'only', 'cannot', 'largest', 'always' or a specific institutional role—often determine the answer. On that basis, option D is the verified answer.