Assignment task:
Define the Lyon hypothesis. Inactivation of a particular X chromosome depends on its genetic content. Inactivated X chromosomes are in some way "marked" such that all clonally related cells have the same X chromosome inactivated. Inactivation of an X chromosome occurs at random early in embryonic development. Inactivated X chromosomes are in some way "marked" such that all clonally related cells have the same X chromosome inactivated. Inactivation of an X chromosome occurs at random just after fertilization. Inactivated X chromosomes are in some way "marked" such that all clonally related cells have the same X chromosome inactivated. Inactivation of a particular X chromosome depends on its genetic content and occurs after differentiation of cell type. Different cell types may inactivate different X chromosomes.