Personally, I think that it's all Mom's side if it truly is genetic hair loss with regards to the androgen receptor. The androgen receptor gene is on the x chromosome, so if there is a defect, then it is obviously inherited from the mother. If it's the result of androgen overproduction or other factor, then I don't consider that to be defective androgen receptor mediated hair loss.
There are probably plenty of men out there with a defective androgen receptor that are protected from its effects by having 5AR enzymes that produce less DHT or they may have more aromatase to convert testosterone to estrogen before it gets converted to DHT.
There are probably some men out there that have relatively normal androgen receptors, but 5AR enzymes that overproduce DHT.
That's a guess, but it sure explains how some guys can suddenly have male pattern baldness with no family history or how it can so efficiently skip multiple generations on the mothers side. Plus, it seems like male pattern baldness is associated with multiple mutations with a possible triplet repeat mutation. That mutation will demonstrate anticipation, which will mean that the disease will be worse with each new generation.
