Comparison of male and female meiotic segregation patterns in translocation heterozygotes: a case study in an animal model (Sus scrofa domestica L.)

BACKGROUND: The comparison of male and female meiotic segregation patterns for individuals carrying identical reciprocal translocations has been rarely reported in mammalian species. The main comparative study involving males and females with comparable genetic background has been performed in the mouse. Swine is another relevant animal model species for meiotic studies. Here we present the segregation patterns determined for sows carrying one of the two following reciprocal translocations: 38, XX, rcp(3;15)(q27;q13), and 38, XX, rcp(12;14)(q13;q21). These segregation data were compared to those previously obtained for closely related boars carrying the same balanced chromosomal rearrangements. METHODS: Dual colour in situ hybridization of whole chromosome painting probes was carried out on metaphases of in vitro-matured oocytes II. Segregation results were obtained for 118 and 206 metaphases II respectively for the two translocations. RESULTS: Significant differences between sexes were demonstrated for both rearrangements. For instance, for the 3/15 translocation, the chromosomally unbalanced gametes were of different origin: preponderance of the adjacent-I segregation in the male (31.4%), and of the adjacent-II (14.3%) and 3:1 (14.3%) segregations in females. For the 12/14 translocation, the proportion of balanced gametes was greater in males than in females (75.9 and 59.4% respectively). CONCLUSION: This study is a new scientific contribution to compare the segregation patterns of male and female carriers of identical chromosomal rearrangements. The results obtained are consistent with those previously reported in mice. Hypotheses to interpret the observed differences between the two translocations, as well as between the male and female segregation patterns, are formulated and discussed.