Some scientists have suggested that it might in some cases be ethically  acceptable to clone existing people. One possibility is generating replacement for a dying  . All such possibilities, however, raise the concern that the clone would be treated as less than a complete individual, because he or she would likely suffer from limitations and expectations based on the family's knowledge of the genetic "twin." Those expectations might be false, because human personality is only partly determined by genes. The clone of an extrovert  could have a quite different way of behavior. Clones of athletes, movie stars, or scientists might well choose different careers because of chance events in early life.        Some people have also put forward the belief that couples in which one member is infertile  might choose to make a copy of one or the other partner. But society ought to be concerned that a couple might not treat naturally a child who is a copy of just one of them. Because other methods are available for the treatment of all known types of infertility, the traditional choice seems more appropriate. None of the suggested uses of cloning for making copies of existing people is ethically acceptable to my way of thinking, because they are not in the interests of the resulting child. It should go without saying that I am strongly opposed to allowing cloned human embryos  to develop so that they can be tissue donors.        In spite of this, it seems clear that cloning from cultured  cells will offer important medical opportunities. Predictions about new technologies are often wrong: societal attitudes change; unexpected developments occur. Time will tell. But biomedical researchers looking into the potential of cloning now have plenty to do. According to the passage, one's personality is determined by   _  .
their genes the environment they live in both their genes and the environment they live in neither their genes nor the environment they live in