Cytogenetic elaboration of a novel reciprocal translocation in sheep.

Reciprocal translocations represent one of the most common structural chromosomal rearrangements observed in both humans and domestic animals. In these translocations, the balanced forms are most frequent but may remain undetected because the carriers show a normal phenotype. For this reason, routine cytogenetic analysis of domestic animals should necessarily rely on banded karyotypes. In fact, during a screening analysis, carried out on phenotypically normal young sheep (Ovis aries, OAR, 2n = 54) from Laticauda-Comisana hybrids, a new structural rearrangement was detected. Two abnormal acrocentric chromosomes (the smallest and the largest one) were found in all metaphases of this carrier animal, suggesting the presence of a reciprocal translocation (rcp). CBA and RBA banding were performed in order to characterize the translocation, and FISH with chromosome-specific BAC probes and telomere probes was applied to confirm the cytogenetic data. The translocation was classified as rcp(4q;12q)(q13;q25).