 Considering the fact that once one X chromosome is inactivated in a cell, all other cells derived from it will have the same X chromosome inactivated, this approach becomes a great tool to differentiate a monoclonal population from a polyclonal one in a female tissue.HUMARA gene, in particular, has three important features that make it highly convenient for the purpose.1-) The gene is located on X chromosome and it goes through inactivation by methylation in normal embryogenesis of a female infant.