It was an interesting programme but having done some reading subsequently it was a bit over-traumatised in my opinion. The contributions largely came from scientists who are, entirely reasonably, pissed off that they weren't listened to at the outset.
Accordingto an interesting article in New Scientist they can test for it in appendices and they apparently screen removed appendices. I read that 1 in 2000 of us probably have the prion protein. What is POSITIVE news though is that based on the number who they think have the protein, and the proportion of people with the MM gene variant, they'd have expected many many more cases in the first wave of young people affected than were actually seen. In other words of the people who are in the hugh risk group and should have exhibited the disease swiftly, only a small proportion were affected.
The significance of the genes is that only the M gene is susceptible to being changed by the prion. Those with VV shouldn't be affected at all. Those with MV could be affected but because they have less M protein to start with the progress of the disease is much slower.