 It can also occur when two fertilized embryo fuse, producing a chimera that might contain two different sets of DNA one XX and the other XY.It could also result from exposure, often in utero, to chemicals that disrupt the normal conversion of the allosomes into sex hormones and further into the development of either ambiguous outer genitalia or internal organs.Ever since the discovery of X-inactivation through research into Calico cats, it has been postulated that X-inactivation plays a role in genetic sex determination in humans.