[quote=Astibus]Please allow me to give you an analogy that will illustrate the underlying problem. Suppose you find yourself in a ping-pong match, where you are standing on one end of the table with the BEST ping-pong racquet you can possibly buy, and a group of people on the other side of the table. Your job is to fend off the balls that these guys are hitting in your direction. Problem is, they have 400 balls at their disposal (symbolizing the 400 possible hereditary diseases). You can easily imagine that eventually, some balls will get through to your side; in the end, I'm sure you'll lose the game - regardless of the quality of your "high-tech"-racquet (or is it racket?) ....... UNLESS........you change the playing field to your advantage (literally). Position the ping-pong table on a hill with a steep slope, so that your opponents will have to hit the balls uphill. :wink: Gravity will play in your favor and return the opponent's balls right back into their quarters. That gravity essentially represents the environmental pressure. If the slope is steep enough, you'll likely succeed.[/quote] Excellent point, Dan. 8) P.S. It's good to know I'm not the only analogy-freak here. :D