In college biology I had to debate Genetically-Modified foods, I was the cons-debator. As I recall, a significant problem with Genetically-Modified plants is that a genetic marker is altered to express a certain trait in a given plant population, but in the process the original marker, which has evolved and endured from the begining of time on earth, is erased or not able to be expressed. The question is what purpose/function did this "erased" marker have---did it protect the plant from a certain fungi or disease?