Practice question

Upon gamete fusion paternal mitochondria located in sperm midpiece enter oocyte cytoplasm along with nucleus and flagellum. Despite entry, sperm mitochondria are targeted for destruction by ubiquitination and mitophagy machinery within early embryo, including recognition by Parkin and LC3 autophagy pathways. Degradation ensures maternal inheritance of mitochondrial genome preventing heteroplasmy and potential incompatibility. By blastocyst stage paternal mtDNA undetectable. This selective elimination explains almost exclusive maternal mitochondrial transmission across generations, with implications for mitochondrial disease inheritance, evolutionary tracking, uniparental inheritance patterns, mitochondrial replacement therapies and genetic counseling paradigms.