Counting zebras

Sleep is essential to all animals with a nervous system, and yet some politicians have considered it a badge of honour that they did not need to indulge in such a trivial activity. The core cellular function of sleep is unknown. Researchers looked at zebra fish across time taking images of chromosomal markers in single cells (Figure). Sleep increased chromosome dynamics in individual neurones that are necessary to reduce the amount of DNA double-strand breaks. During wakefulness, chromosome dynamics are low and the number of these double-strand breaks accumulates. These results establish chromosome dynamics as a …