It has been proven that there is one gene that causes a disease called Hutchinson-Gilford progeria. It makes children age so fast that by 5 they lose their hair, become wrinkled and develop cardiovascular disease. They look like little old men and women. And they die at about 12. A different gene causes Huntington's disease. Symptoms begin when people are in their 30s or 40s, after they have finished reproducing. There are only a few dozen children in the world with progeria. There are tens of thousands of people with Huntington's disease.