Ohno’s finding suggested to me that the reason that females had no more G6PD than males might be that only one of the 2 X-chromosomes was active (Figure 5). Thepattern of inheritance suggested that it could not always be either
the maternally derived or paternally derived X-chromosome thatwas inactivated, and that inactivation must occur early in embryogenesis,presumably when the Barr chromatin body (representing the
condensed X-chromosome) appeared.