I didn't think it was comparable like that?

( Jenk Neptune is a pedant and now I can't fit my sig in, Wed 27 May 2009, 19:26, archived)

yes it is
the only difference between this and a mutation that prevents parkinson's disease (assuming both are dominant traits with the same number of genes involved the activation) is that this is easily observed
( Lightguy hail satan, Wed 27 May 2009, 19:36, archived)