I believe it is exactly the mechanism described in the article: X-inactivation is incomplete. Some of the genes on the "inactivated" chromosome remain active.

I believe it is exactly the mechanism described in the article: X-inactivation is incomplete. Some of the genes on the "inactivated" chromosome remain active. What is new in this article is that they connected specific genes known to be active, to genes relevant for cancer. In other words, the theory was that the remaining-active genes helped avoid cancer, color-blindness, etc., and the article provides strong evidence supporting that in the area of cancer, the genes are the right ones. Wikipedia suggests there are other theories too, like inactivating picking the "best" of the two options non-randomly, and the mosaic effect - it isn't the same X-chromosome inactivated everywhere, so e.g. some retinal cells might have one X and others the other. https://en.wikipedia.org/wiki/X-inactivation#Selection_of_one_active_X_chromosome https://en.wikipedia.org/wiki/X-inactivation#Selection_of_on...