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
EYE SPY A new citizen science project needs volunteers to help identify protein molecules in micrographs (right image is the same micrograph as the left, except with the proteins circled).
REPLACEMENT REFINED Researchers have improved a technique that transfers pronuclei (round craters, center) from an egg with diseased mitochondria to a donor egg with healthy mitochondria.