thymidine kinase (tk) gene

thymidine kinase (tk) gene

a gene coding for thymidine kinase that is expressed in most mammalian cells and some viruses (herpes-, pox-viruses). Used as a selectable marker in that tk minus (tk) cells and viruses do not survive in medium containing hypoxanthine, aminopterin and thymidine (HAT medium); such cells cotransfected with a vector carrying a tk gene (tk+) can be rescued.