Possibilties

   There are three different chances of a parent passing on Tay Sachs disease to their children. Fifty percent of chances are that their child will be a carrier, but not have the disease. Twenty-five percent of chances are that their child will not be a carrier and not have the disease. Lastly, the other twenty-five percent of chances will be that their child will have the disease. 

   For instance, if two parents are carriers of Tay Sachs disease their child would most likely have it. Another example is if only one of the parents have the disease, the outcome will either good or bad. The child come out with the disease or not have it at all.