What clever girls you are,I personally don't have a clue about the mdr2 gene/bsc way above my head,I totally agree that a fearful mum may breed a fearful pup but so also think that just a good owner could sort that out with a bit of understanding.I meet lots of people with many different dogs down the woods on a daily basis,most of the dogs are friendly a few are iffy??but the ones that are iffy have all had previous issues like being rescued from a terrible home.I also think that just some dogs are not good because of??? Like us people most of us humans are good people but there are a few out there that are dangerous for what reason bad upbringing or a funny type gene or just born that way who knows. 1 of the trainers at Xena's school has a collie that is nasty to every dog her owner has no idea why and indeed I had one dog that hated every dog wonderful with people and every attempt was made to sort it failed for me but I was aware of it and just avoided the whole situation.I think certain breeds have a tendency to be unpredictable but also think that most dogs can be also,only good understanding owners that really love there dogs will be aware,guess I am totally wrong on this as one can buy a pup any where and never quite know how he/she will turn out.Kristina