📘Q.2 IAS Prelims 2021 — GS | Science & Technology |Mitochondrial Diseases & Replacement Therapy
🧑🏫 Authentic Classroom Explanation by IAS Monk
🧬 Q2. Mitochondrial Diseases & Replacement Therapy
📌 Question
In the context of hereditary diseases, consider the following statements:
- Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg.
- 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
(d) Neither 1 nor 2
✅ Correct Answer: (c) Both 1 and 2
🧑🏫 Authentic Classroom Explanation by IAS Monk
From first principles to final option — the UPSC way.
🔍 Concept First
Mitochondria possess their own DNA (mtDNA), separate from nuclear DNA. Disorders in mtDNA cause mitochondrial diseases, often severe and inherited.
🔬 Statement-wise Analysis
Statement 1:
Passing on mitochondrial diseases can be prevented by mitochondrial replacement therapy (MRT) before or after IVF.
✔️ Correct
- Mitochondrial Replacement Therapy (MRT) replaces defective maternal mitochondria with healthy donor mitochondria
- Techniques include:
- Spindle Transfer (ST)
- Pronuclear Transfer (PNT)
- Polar Body Transfer (PBT)
- This is done before embryo development, either before or shortly after fertilisation
👉 Objective: prevent transmission of lethal mitochondrial disorders
Statement 2:
A child inherits mitochondrial diseases entirely from the mother.
✔️ Correct
- In humans, mitochondrial DNA is maternally inherited
- Paternal mitochondria are typically destroyed after fertilisation
- No convincing evidence of paternal mtDNA transmission in humans
🔍 Curiosity Raiser
Did you know?
A child born through mitochondrial replacement therapy technically carries genetic material from three individuals — nuclear DNA from parents and mitochondrial DNA from a donor.
🧠 Enrichment Notes (UPSC Lens)
- Mitochondrial DNA ≠ Nuclear DNA
- mtDNA controls cellular energy production
- Mutations affect high-energy organs: brain, muscles, heart
- Why UPSC likes this topic:
- Intersection of genetics + ethics + biotechnology
- Frequently in news due to “three-parent baby” debates
- Trap to avoid:
- Assuming father contributes mitochondrial genes (❌)
- Exam Value:
- Tests understanding of inheritance mechanisms, not just terminology
🪶 IAS Monk Closing Whisper
Not all inheritance flows through chromosomes — some travels through energy itself.