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
TOUGH BITE Deer ticks are now spreading a new species of bacteria that causes Lyme disease.
UNCOOL DROOL Studies of drug-resistant urinary tract infections in dogs and cats raise concerns that pets might contribute to the spread of drug-resistant microbes.
Scientists have identified a protein that chops up the mitochondrial DNA in a dad’s sperm after it fertilizes an egg. The finding helps explain why mitochondrial DNA is usually passed on only by mothers.