SINCE 1949, Barr et al. and others 1–3 have described the presence of ‘sex chromatin’ in various tissues of several animal species, arriving at the conclusion that in all of them behaviour ...

The rat is a medium-sized rodent from the genus Rattus. Rattus norvegicus (brown rat) is a model vertebrate reared in the laboratory for studying subjects such as genetics, physiology, disease and ...

Science Photo Library Has the black rat (Rattus rattus) been falsely blamed for spreading plague during the Black Death? "We have good mortality data from outbreaks in nine cities in Europe," Prof ...