A clone is just a cutting that takes root seperate from the mother. Same DNA, same integrity. Stress from the transplant, if not done properly, can lead to a lower yield and overall decline in the healthiness of the plant. If done in a proper manner the cuttings will simply be a seperate plant of the same strain. If DNA is altered in even the slightest way, the plant will die. DNA is a very sensitive thing. Use yourself as a constitution to this. One of your cells is exposed to too much UV rays, the radiation alters your DNA in the slightest bit, you now have cancer. The idea of DNA weakening is absurd. DNA is a complex of molecules which are composed of atoms and from my few years of chemical engineering I haven't encountered any weak atoms of any element.