CHARACTERIZATION OF A TRANSLOCATION AND ITS IMPACT ON FERTILITY IN THE PIG

A chromosome anomaly originally detected in two intersex pigs and prev iously reported as a Robertsonian translocation was characterized, and its transmission pattern was assessed by analyzing the progeny and im mediate relatives of a sow. Cytogenetic investigations on four phenoty pically normal relatives of the intersexes, including a sow, showed th at the rearrangement was a reciprocal translocation involving the X ch romosome and an autosome. Giemsa-banding and reverse-banding technique s indicated that the break in the X chromosome may have occurred in th e terminal segment of the short arm (Xp) and that in the autosome in t he proximal segment of the acrocentric chromosome 14 (14q). Reverse-ba nding techniques also revealed that the normal X is the late-replicati ng X in female translocation carriers. Centromere banding revealed an intercalary band on the long arm of the submetacentric chromosome repr esenting the altered X in translocation carriers. The translocation wa s designated as rep (X;14) (p+;q-). Chromosome analysis on 45 of 72 li ve offspring of the carrier sow showed a 20:25 distribution of carrier s to normal piglets, with a carrier to normal ratio of 5:13 among fema les and 15:12 among male piglets, indicating an overall reduction of f emales (18) compared with males (27). Male carriers from one litter at sexual maturity showed hypoplastic testes and no spermatozoa in their ejaculates or fluid aspirates from the cauda epididymis. Their semini ferous tubules were narrow, spermatogenesis was impaired, and pyknotic and giant nuclei were abundant in the germinal epithelium. Meiotic pr eparations showed no stage beyond pachytene, suggesting that the absen ce of spermatozoa in the ejaculates may be due to the arrest of cells at the pachytene stage.