Scientists find clue to why mitochondrial DNA comes only from mom
Protein destroys contribution from dad’s sperm, study in worms shows
![cell and fertilized egg with mitochondria](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2016/06/062316_lh_dad-mitochondria.jpg?fit=860%2C460&ssl=1)
BREAK DOWN Like most cells, sperm contain energy-producing mitochondria (one organelle and its membrane (red circle) shown, left). Once a sperm fertilizes an egg, the sperm’s mitochondria break down inside that membrane (right).
Q. Zhou et al/Science 2016