Location of the X inactivation center in primates and other mammals.

In humans, the X chromosome inactivation center and an X inactivation-associated metaphase fold are at the same location (bands Xq13----21) or are very closely associated. In other mammals, the location of the X inactivation center is unknown, but it has been suggested that the relationship between the inactivation center and the inactivation-associated fold may make it a useful marker for both identifying the inactivated X and locating the inactivation center in other mammalian species. If a similar metaphase fold is present in other mammals, the inactivation center would be located at the same site or very nearby. All of nine primate species did express an inactivation-associated fold. In most, the fold was located at the band homologous to human Xq13----q21. In one of two chimpanzees, band Xq23----q24 was implicated. In five other mammals an inactivation-associated fold was observed, but in two species, no fold was observed.