Contents

07 May 2021
Vol 372, Issue 6542

About The Cover

Cover image expansion

COVER A young creeping vole (Microtus oregoni) moves cautiously through the forest in Olympic National Park, United States. In this species, the standard mammalian sex determination system has been rearranged, such that there is no standard Y chromosome, yet Y chromosome genes are present in both sexes. The creeping vole genome reveals rare divergence from the relatively inflexible mammalian sex determination system. See page 592.
Photo: David Moskowitz