Cloning also involved someone being the donor of DNA to create a clone. A clone had DNA identical to the donor's, but certain cloning techniques caused a genetic degeneration, which could be detected. (DS9: "A Man Alone") In 2268, Spock volunteered to be the blood donor for a blood transfusion to facilitate his father's heart surgery. (TOS: "Journey to Babel" ) In 2366, Worf was the only suitable ribosome donor to save Patahk; Worf refused to donate and the Romulan ultimately died. (TNG: "The Enemy" )