'Both X-chromosomes in a female have an equal chance of becomes a Barr body in each cell.' Every source I can find on Barr bodies claims this and I can think of no reason for why it may be wrong. What I want to know is if anyone has empirically tested this. Has anyone ever taken a model organism, measured the distribution of Barr bodies, and calculated exactly how far the result is from the 1:1 ratio that the theory predicts? Has anyone ever tested the Null Hypothesis of this statement, or has it just been accepted based on the theory alone?