Meiosis and spermatogenesis in bulls heterozygous for a presumptive 1/29 Robertsonian translocation

Abstract

Bulls heterozygous for the 1/29 Robertsonian translocation showed normal mating behavior, semen quality and spermatogenesis. The karyotypes of 90 offspring of 1 heterozygous bull were consistent with a normal 1:1 segregation of the translocation. There was no difference in overall chiasma frequency at diakinesis between heterozygous and normal bulls, and while a trivalent did not appear to be altered when compared with that found in the normal No. 1 bivalent. An increased frequency of aneuploid secondary spermatocytes at the 2nd meiotic division (M II) was found in the heterozygous bulls, the rate of nondisjunction based on the proportion of hypermodal cells being raised from 2.8% in the normal to 6.4% in the heterozygous animals.