Question 6 from UPSC CSE 2021 - S&T

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 an egg.
2. A child inherits mitochondrial diseases entirely from the mother and not from the father.
Which of the statements given above is/are correct?

Accepted Answer

Correct Option: C. Both 1 and 2

Strategy: Focus on keywords: 'mitochondrial replacement therapy' and inheritance pattern. Recall that mitochondrial diseases are passed through maternal mtDNA, and therapy seeks to prevent transmission. Statement 1 is supported by understanding that MRT works both pre- and post-fertilization. Statement 2 aligns with the well-known fact that mitochondria, and thus their associated diseases, are maternally inherited in humans. Both statements match established scientific facts.

Key Info: **Inheritance Pattern**
Mitochondrial diseases stem from mutations in mitochondrial DNA (mtDNA), essential for cellular energy production. In humans, mtDNA is inherited almost exclusively from the mother because sperm mitochondria are typically destroyed after fertilization. Paternal transmission is exceptionally rare and not consistently observed.

**Therapy Techniques**
Mitochondrial Replacement Therapy (MRT) uses assisted reproductive techniques to prevent the transmission of these disorders by replacing defective mitochondria with healthy donor ones.
-   Spindle transfer (ST)
-   Pronuclear transfer (PNT)
-   Polar body transfer (PBT)

**Application and Goal**
MRT can be applied before fertilization (to the egg) or after fertilization (to the zygote), though regulations differ by country. The goal is to enable mothers with mtDNA mutations to have genetically related children without the risk of passing on severe mitochondrial diseases, which can cause metabolic, muscular, or neurological problems.

Answer

Option A: 1 only

Answer

Option B: 2 only

Answer

Option D: Neither 1 nor 2