The bottom line is that there are something like 20 or more genetic markers that it is strongly believed by current research make an individual more susceptible to developing Crohns when they come in contact with one of a wide range of possibke environmental triggering factors (bacteria likely). Many of those genetic markers are more prevalent in some ethnic populations, including Jewish, but they are by no means resticted to them. A good analogy is the collection of genes that make one susceptible to developing alcoholism if one drinks -- more prevalent in Indian, irish and some northern European lines of descent, but not restricted to them. Your father is simply misinformed. You can and likely do have a collection of genetic factors that made you more prone to CD, but if it makes him feel better, only half (at most) would come from him, since you also have half of your mother's genes (and a quarter of each grandparent's, etc.) In fact, it is a dead certainty that each of us carries dozens, if not hundreds, of genes that make us more susceptible than average (and also less susceptible that average) to a huge range of medical and physiological conditions. It may be that he has a genetic proclivity to vain narrow mindedness . . .