Librarian's Comment : Quite often in the literature, the importance of sex chromosomes is reduced to their pivotal role in reproductive functions. Yet, all our cells harbor the X (and the Y in males). For a long time, it has been assumed that intrinsic sex-specific differences in non-reproductive phenotypes (ex: higher incidence of cancer in men) are solely the consequence of the different hormonal environment between women and men. However, recent observations across several species have begun to question this postulate. As a result, a hypothesis has emerged where the X and Y can, by themselves, generate somatic sex differences independently of hormonal cues. The possibility that sex chromosomes can affect somatic cell function throughout life can have major implications not only for our understanding of sexual dimorphism, but also from a clinical perspective (at the pharmacokinetic level, for instance).