Loidl J
Institute of Botany, University of Vienna, Austria.
Genetics. 1995 Apr;139(4):1511-20. doi: 10.1093/genetics/139.4.1511.
Meiotic chromosome pairing in isogenic triploid and tetraploid strains of yeast and the consequences of polyploidy on meiotic chromosome segregation are studied. Synaptonemal complex formation at pachytene was found to be different in the triploid and in the tetraploid. In the triploid, triple-synapsis, that is, the connection of three homologues at a given site, is common. It can even extend all the way along the chromosomes. In the tetraploid, homologous chromosomes mostly come in pairs of synapsed bivalents. Multiple synapsis, that is, synapsis of more than two homologues in one and the same region, was virtually absent in the tetraploid. About five quadrivalents per cell occurred due to the switching of pairing partners. From the frequency of pairing partner switches it can be deduced that in most chromosomes synapsis is initiated primarily at one end, occasionally at both ends and rarely at an additional intercalary position. In contrast to a considerably reduced spore viability (approximately 40%) in the triploid, spore viability is only mildly affected in the tetraploid. The good spore viability is presumably due to the low frequency of quadrivalents and to the highly regular 2:2 segregation of the few quadrivalents that do occur. Occasionally, however, quadrivalents appear to be subject to 3:1 nondisjunction that leads to spore death in the second generation.
对酵母同基因三倍体和四倍体菌株中的减数分裂染色体配对以及多倍体对减数分裂染色体分离的影响进行了研究。发现粗线期联会复合体的形成在三倍体和四倍体中有所不同。在三倍体中，三价联会，即在给定位点上三个同源染色体的连接很常见。它甚至可以沿着染色体一直延伸。在四倍体中，同源染色体大多形成配对的二价体。多价联会，即在同一区域内两个以上同源染色体的联会，在四倍体中几乎不存在。由于配对伙伴的切换，每个细胞中大约出现五个四价体。从配对伙伴切换的频率可以推断，在大多数染色体中，联会主要在一端开始，偶尔在两端开始，很少在额外的中间位置开始。与三倍体中孢子活力显著降低（约40%）相比，四倍体中的孢子活力仅受到轻微影响。良好的孢子活力可能是由于四价体的频率较低以及少数出现的四价体高度规则的2:2分离。然而，偶尔四价体似乎会发生3:1的不分离，导致第二代孢子死亡。
