🧑‍🏫 Authentic Classroom Explanation by IAS Monk

🧬 Q2. Mitochondrial Diseases & Replacement Therapy

📌 Question
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
(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.