UPSC Prelims 2020 Q37: Science & Technology – Biotechnology & Genetics
- (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
Answer: (d) prevention of mitochondrial diseases in offspring
Explanation
Pronuclear Transfer: Biotechnology Application
| Option | Is Pronuclear Transfer used for? |
|---|---|
| In vitro fertilization (egg + sperm) | No - that's standard IVF |
| Genetic modification of sperm-producing cells | No - uses pronuclei, not somatic cells |
| Development of stem cells into embryos | No - different from pronuclear transfer |
| Prevention of mitochondrial diseases | YES |
Pronuclear Transfer (PTT): Advanced technique to prevent mitochondrial inheritance disorders.
- Take egg nucleus (containing mitochondrial disease DNA)
- Remove nucleus from donor egg (healthy mitochondria)
- Insert patient's nucleus into donor's cytoplasm (inherits healthy mitochondria)
- Fertilize + implant
- Results in child with patient's nuclear genes but donor's healthy mitochondria
Used for conditions like MELAS, Leigh syndrome (mitochondrial DNA mutations).
Answer: (d) prevention of mitochondrial diseases in offspring.
Why each option is right or wrong
- (a) Incorrect. That's standard IVF, not pronuclear transfer.
- (b) Incorrect. Pronuclear transfer targets mitochondria, not sperm-producing cells.
- (c) Incorrect. Stem cell differentiation is separate from pronuclear transfer.
- (d) CORRECT. Pronuclear Transfer is used to prevent mitochondrial diseases by transferring healthy mitochondria from donor egg to patient's nuclear DNA.
Key point
Pronuclear Transfer (PTT) for mitochondrial disease prevention: Replace mitochondria (which are maternally inherited) with healthy versions. Allows carrier parents to have unaffected children. UK approved PTT (2015) - first case born 2016.
Remember
In the context of human reproductive technology, 'Pronuclear Transfer' is used for the PREVENTION OF MITOCHONDRIAL DISEASES IN OFFSPRING by replacing defective mitochondria (inherited from mother) with healthy mitochondria from a donor while preserving the patient's nuclear DNA.
Common mistakes
- Confusing PTT with regular nuclear transfer/cloning. PTT targets mitochondria specifically.
- Assuming mitochondrial diseases can be treated by fixing nuclear genes. Most inherit maternally via mitochondria, so mitochondrial replacement is key.
- Missing the ethical debates around PTT - 'three-parent babies' (nuclear DNA from 2 parents, mitochondria from donor).
Exam tip
Mitochondrial inheritance: Mitochondria inherited from mother (maternal inheritance). Mitochondrial diseases (~1:4000 births) can be severe (muscle weakness, heart disease). PTT is targeted prevention - not general genetic engineering.
Sources
- Human Fertilisation and Embryology Authority (HFEA) - Mitochondrial Replacement Guidance
- Dieter Egli et al. - Reprogramming within Hours and the Relevance of Altered Epigenetic Memory