Thymidine triphosphate (TTP), also called deoxythymidine triphosphate (dTTP), is one of the four nucleoside triphosphates that are used in the in vivo synthesis of DNA. Unlike the other deoxyribonucleoside triphosphates, thymidine triphosphate does not always contain the "deoxy" prefix in its name. This is because dTTP does not have a corresponding ribonucleoside triphosphate, as the uridine triphosphate, which lacks thymidine's 5-methylation, is used instead.