BAC clone RP23-223G1 containing the mouse Fut1, Fut2, and Sec1 loci was manipulated through Red/ET recombination technology. In this targeted mutation, an FRT-flanked hygromycin resistance gene was used to replace the coding region of Fut1. The BAC was also modified to contain a deletion, Del(7Fut2-Sec1)1Dzhou (J:278494)