The Thrombin (prothrombin) gene is located on the eleventh chromosome (11p11-q12). The molecular weight of prothrombin is approximately 72000 gmol^-1. The catalytic domain is released from prothrombin fragment 1.2 to create the active enzyme thrombin, which has a molecular weight of 36000 gmol^-1.There are an estimated 30 people in the world that have been diagnosed with the congenital form of Factor II deficiency, which should not be confused with a mutation of prothrombin.