In a conference abstract, Haton et al. (2000) reported that, by cloning and sequencing a very likely comparative candidate gene (based on the homologous human disorder), they had identified a 76-bp insertion in exon 12 of the Factor XI gene as being causative of Factor XI deficiency in Holstein cattle. This discovery was fully described by Marron et al. (2004) who explained that "This insertion introduces a stop codon that results in a mature FXI protein lacking the functional protease domain encoded by exons 13, 14 and 15." A second insertion (involving 15 bp in exon 9 of the same gene, together with "a single-nucleotide substitution of C to A at the insertion site") was reported in Japanese Black cattle by Kunieda et al. (2005). The best way to designate this variant is to regard it as a delins, comprising a 1bp (C) deletion and a 16bp insertion, with the insert ending in A, i.e. g.16305660delinsATATGTGCAGAATATA. Mondal et al. (2016) reported the 76bp insertion variant in Sahiwal cattle.
