Abstract
The chromosome constitutions of three cases of bovine freemartins were observed in blood cultures as well as in tissue cultures from various organs. In both freemartins and their co-twins (case A-C), tissue cells of mesodermal and endodermal origin generally showed 2A-XX/2A-XY mosaicism. A normal cow from the non-freemartin dizygotic twins possessed a normal female complement of chromosomes (case D).
