A 14/20 Robertsonian translocation in Swiss Simmental cattle

A chromosomal abnormality identified as a 14/20 Robertsonian translocation by measurement and banding studies has been found randomly in several Swiss Simmental cattle. These cases have all been traced back to one ancestral bull. The testicular function of three unselected male offspring, two heterozygotes and one normal was studied. All possessed apparently normal spermatogenesis. In a meiotic study no alteration of overall chiasma counts were found at diakinesis in the heterozygous bulls compared with the normal, while the presence of a trivalent confirmed the diagnosis of a Robertsonian translocation. Also in the heterozygotes a small number of secondary spermatocytes were identified but they were too few to draw any firm conclusions regarding alterations in non disjunction rate.