In the context of hereditary diseases, consider the following statements:
- Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg.
- A child inherits mitochondrial diseases entirely from mother and not from father.
Which of the statements given above is/are correct?
Detailed Explanation:
Answer: Option 3 — Both 1 and 2
Mitochondrial replacement therapy (MRT) is a reproductive technique designed to prevent the transmission of mitochondrial diseases from mother to child by replacing defective mitochondria with healthy donor mitochondria, either before or after in vitro fertilization. Mitochondrial DNA is inherited exclusively through the maternal line, as mitochondria in sperm are typically destroyed after fertilization, making it impossible for a child to inherit mitochondrial diseases from the father.
✅ Statement 1 – Correct: MRT can be performed either before fertilization (using maternal spindle transfer) or after fertilization (using pronuclear transfer) to prevent mitochondrial disease transmission.
✅ Statement 2 – Correct: Mitochondrial DNA is inherited entirely from the mother, as only the egg contributes mitochondria to the embryo.
📝 Short Notes: Mitochondrial Inheritance and Replacement Therapy
| Aspect | Details |
|---|---|
| Mitochondrial DNA (mtDNA) | Circular DNA present in mitochondria; encodes 37 genes essential for cellular energy production; inherited exclusively from mother |
| Mitochondrial Diseases | Caused by mutations in mtDNA; affect energy production in cells; examples include MELAS syndrome, Leigh syndrome, and Leber's hereditary optic neuropathy |
| Maternal Inheritance | Sperm mitochondria are destroyed after fertilization; only egg mitochondria contribute to embryo; thus, mtDNA comes only from mother |
| Mitochondrial Replacement Therapy (MRT) | Technique to prevent transmission of mitochondrial diseases; involves replacing defective mitochondria with healthy donor mitochondria |
| MRT Techniques | Maternal Spindle Transfer: Before fertilization - nucleus from mother's egg transferred to enucleated donor egg with healthy mitochondria Pronuclear Transfer: After fertilization - pronuclei from fertilized egg transferred to enucleated donor embryo |
| Three-Parent Baby | Child born through MRT has genetic material from three people: nuclear DNA from both parents and mtDNA from donor |
| Ethical and Legal Status | UK became first country to legalize MRT in 2015; debate continues in many countries regarding ethical implications |
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