Question 22 from UPSC CSE 2020 - S&T

Question

In the context of recent advances in human reproductive technology, 'Pronuclear Transfer' is used for

IASCODEX · Accepted Answer

Correct Option: D. prevention of mitochondrial diseases in offspring

Strategy: - Identify 'Pronuclear Transfer' as the core concept.
- Connect it specifically to the prevention of mitochondrial diseases, its primary application.
- Rule out unrelated options like general IVF, gene editing, or stem cell research, as they don't involve pronuclear-stage manipulations.
- Rely on direct recall of pronuclear transfer's role in mitochondrial replacement.

Key Info: ## Pronuclear Transfer: An Overview
Pronuclear transfer is an assisted reproductive technique aimed at preventing mitochondrial diseases. These genetic disorders stem from mutations in mitochondrial DNA (mtDNA), inherited exclusively from the mother.

### Process
1.  **Zygote Creation:** Two fertilized eggs (zygotes) are formed: one from the intending parents (who may carry defective mtDNA) and another from a healthy donor.
2.  **Pronuclei Removal:** Before cell division, the nuclear material (pronuclei) is extracted from both zygotes.
3.  **Transfer:** The parents' pronuclei are then transferred into the donor zygote, which has had its own pronuclei removed but still contains healthy mitochondrial DNA.
4.  **Result:** The reconstructed zygote holds the parents' nuclear DNA and the donor's healthy mitochondria, thereby preventing the transmission of mitochondrial disorders such as Leigh syndrome or MELAS.

### Key Characteristics
*   A form of mitochondrial replacement therapy, similar to spindle transfer.
*   Does not alter nuclear genes.
*   Not used for direct gene editing or for the fertilization process itself.

### Regulatory and Ethical Context
Pronuclear transfer involves significant regulatory approval and ethical considerations. In some countries, like the UK, these therapies are permitted under stringent conditions.

IASCODEX · Answer

Option A: fertilization of egg in vitro by the donor sperm

IASCODEX · Answer

Option B: genetic modification of sperm producing cells

IASCODEX · Answer

Option C: development of stem cells into functional embryos