Centric fusion translocations in cattle: a review.

The incidence of centric fusion (Robertsonian) translocation in cattle breeds is reviewed. Thirteen different centric fusions have been identified in cattle, with few breeds carrying more than one translocation. Of the commercial breeds, Friesian-Holstein cattle appear to be free of translocations, while the Simmental is the only one which carries three translocations. The major effect of centric fusion is on fertility, causing unbalanced gametes and hence unbalanced zygotes to be formed, leading to early embryonic death. However, to discard all translocation-carrying animals may be misguided as they represent genetic variation and a source of desirable traits.