In the context of recent advances in human reproductive technology, "Pronuclear Transfer" is used for
- (a) fertilization of egg in vitro by the donor sperm
- (b) genetic modification of sperm producing cells
- (c) development of stem cells into functional embryos
- (d) prevention of mitochondrial diseases in offspring ✓ UPSC's answer
Why the answer is (d)
• Pronuclear transfer is a form of mitochondrial replacement therapy: after IVF, the pronuclei (nuclear DNA) of the parents' fertilised egg are moved into a donor's fertilised egg whose own pronuclei have been removed but whose mitochondria are healthy.
• The child thus inherits nuclear DNA from both parents and mitochondrial DNA from the donor, preventing maternally inherited mitochondrial diseases — option (d).
• The UK approved mitochondrial donation in 2015; the first birth from a related method (spindle transfer) was reported in 2016, and UK births using pronuclear transfer were reported in 2023.
• It is not about donor-sperm fertilisation (a), editing sperm-producing cells (b) or stem-cell embryos (c).
• Hence option (d).
Why the other options are wrong
- (a) fertilization of egg in vitro by the donor sperm
- Donor-sperm IVF is ordinary assisted reproduction, not pronuclear transfer.
- (b) genetic modification of sperm producing cells
- It does not modify sperm-producing cells.
- (c) development of stem cells into functional embryos
- It does not turn stem cells into embryos.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.