Why is amputation necessary in cases of gangrene? What is aspartame and can it cause Alzheimer's? What's the basis of the Atkins Diet? How is melanin made and is neuromelanin the same stuff? Why do objects in the rear view mirror appear closer than they are? Are insecticidal deaths painful for insect victims? Why does booze cause a ruddy complexion? And at what age do babies begin to think? Join Dr Chris for another round up of top quality questions from South Africa...