In the context of hereditary diseases, consider the following statements : 1. Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg. 2. A child inherits mitochondrial diseases entirely from mother and not from father. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2 ✓ UPSC's answer
- (d) Neither 1 nor 2
Why the answer is (c)
• Mitochondria carry their own DNA, and only the egg's mitochondria pass to the embryo; sperm mitochondria are destroyed after fertilisation.
• Statement 2 is correct: mitochondrial diseases are therefore inherited entirely from the mother.
• Statement 1 is correct: mitochondrial replacement therapy transfers the mother's nuclear DNA into a donor egg with healthy mitochondria — either before fertilisation (maternal spindle transfer) or after (pronuclear transfer), producing a 'three-parent' baby.
• The UK legalised MRT in 2015; the first such births were reported in 2016.
• Hence both 1 and 2, option (c).
Why the other options are wrong
- (a) 1 only
- Statement 2 is also correct: mitochondrial DNA comes only from the mother.
- (b) 2 only
- Statement 1 is also correct: MRT works before or after IVF.
- (d) Neither 1 nor 2
- Both statements are correct.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.