The blood type from an individual can be of critical importance and is determined before birth. One gene copy comes from each parent, combining to determine blood type by causing proteins called agglutinogens to exist on the surface of red blood cells. If an incompatible type of blood enters a body through a transfusion, special antibodies, known as agglutinins, in the recipient's blood will attack the foreign blood and cause blood clots to form. Although stringent testing methods are implemented, accidents do occur and transfusion patients sometimes receive the wrong blood type. In hopes of alleviating the risk, scientists are trying to find ways to chemically convert all donated blood into type O, which is compatible with all blood types.