Bar bodies in the mouse.

Abstract

UP to the present, sex chromatin has not been identified in the nuclei of mouse cells. This is probably due to the fact that such nuclei contain multiple chromocentres, of varying size and number, the presence of which tends to mask the appearance of a sex-specific chromatin mass in females. Moore and Barr1, in a systematic survey of the nerve cell nuclei of many different mammals, were unable to demonstrate sexual dimorphism in those of the mouse. Later, Hay2, examining twenty non-nervous tissues of the mouse, could not identify sex chromatin in any of them. Himrichsen and Gothe3 analysed the multiple chromocentres of murine Purkinje cells, organizing them into eleven arbitrary patterns in accord with their sizes and distribution. Among these patterns there were two configurations with respect to which male and female mice seemed to differ, but neither of these was that of the single nucleolar satellite common to the neurones of female mammals.