Commercial growers do not use potato seeds because it takes a long while to establish the plant and when they do grow they produce smaller tubers. Also, there is a genetic variation among the seedlings. So what your seed grows will be totally different than the original plant. However once in awhile you can obtain a new potato variety by using this method.
WARNING: Potato fruits are high in solanine, a substance that is toxic to humans, particularly children. Potato fruits should not be eaten, no matter how much they look like tomatoes!