Bouvet A, Popescu C P, de Giovanni-Macchi A M, Colombo G, Molteni L
INRA-CRJ Laboratoire de Cytogénétique, Jouy-en-Josas, France.
Ann Genet. 1989;32(4):193-9.
Synaptonemal complexes analysis was performed using electron microscopy on surface-spread spermatocytes of a bull heterozygous for the 4;8 Robertsonian translocation. In 19 cells examined, the longest autosomal complex showed kinetochores in a central position whereas the remaining autosomal complexes showed terminal kinetochores. Synapsis in the trivalent appeared complete in all cells, and the trivalents usually showed a CIS configuration. The arm ratio varied from 1.05 to 2.04 with an average of 1.32 +/- 0.43. Out of 47 cells showing X-Y bivalents, 34 showed a small synaptonemal complex at one extremity of the X chromosome, and an unstained gap in the Y chromosome. There was no association between the X-Y bivalent and the trivalent. The absence of association would explain the normal spermatogenesis noted in this bull, in contrast to human and mouse carriers of translocations which show impaired spermatogenesis due to the association between the rearranged chromosomes and the sex vesicle. Further studies involving bulls carrying one or more Robertsonian translocations are needed to determine whether this absence of association is a constant feature in cattle.
利用电子显微镜对一头携带4;8罗伯逊易位杂合子的公牛的表面铺展精母细胞进行联会复合体分析。在检查的19个细胞中，最长的常染色体复合体的着丝粒位于中央位置，而其余常染色体复合体的着丝粒位于末端。在所有细胞中，三价体的联会似乎都是完整的，并且三价体通常呈现CIS构型。臂比在1.05至2.04之间变化，平均为1.32±0.43。在47个显示X-Y二价体的细胞中，34个在X染色体的一端显示出一个小的联会复合体，而Y染色体上有一个未染色的间隙。X-Y二价体与三价体之间没有关联。这种无关联现象可以解释该公牛精子发生正常的情况，这与人类和小鼠易位携带者不同，后者由于重排染色体与性泡之间的关联而表现出精子发生受损。需要对携带一个或多个罗伯逊易位的公牛进行进一步研究，以确定这种无关联现象在牛中是否是一个恒定特征。
