RECIPROCAL CHROMOSOME-TRANSLOCATION, RCP(7-17)(Q26-Q11), IN A BOAR GIVING REDUCED LITTER SIZE AND INCREASED RATE OF PIGLETS DYING IN THE EARLY-LIFE

Cytogenetic investigations in a boar causing a 41% reduction in litter size and also producing piglets that died soon after birth revealed t he presence of a reciprocal chromosome translocation, rcp(7;17)(q26;q1 1). The translocation resulted in one extremely small telocentric chro mosome marker. Synaptonemal complex analysis of spread spermatocytes b y electron microscopy revealed an unusual behaviour of the translocati on. This formed not only different types of quadrivalents (78.1% of th e cells), similar to those previously found in boars heterozygous for reciprocal exchanges, but also completely or incompletely paired triva lent configurations, plus univalent (21.9%). Association between the s ex bivalent and the translocation configuration was observed (18.7%), but testicular histology was normal. Furthermore, the boar with the tr anslocation was found to produce tertiary monosomy and trisomy in some of the liveborn piglets. Some of the tertiary monosomic offspring, wh ich died in the early extra-uterine life, demonstrated ventricular sep tal defect and cleft palate.