QUOTE : Mary cringed every time she read a popular article that tried to explain why mitochondrial DNA is only inherited from the maternal line. The explanation usually given was that only the heads of sperm penetrate eggs, and only the midsections and tails of sperm contain mitochondria. But although it was true that mitochondria were indeed deployed that way in sperm, it wasn’t true that only the head made it into the ovum. Microscopy and DNA analyses both proved that mtDNA from the sperm’s midsection does end up in fertilized mammalian eggs. The truth was no one knew why the paternal mitochondrial DNA isn’t incorporated into the zygote the way maternal mitochondrial DNA is; for some reason it just disappears