Winking H, Reuter C, Traut W
Institut für Biologie der Medizinischen Universität Lübeck, Germany.
Chromosome Res. 1993 May;1(1):37-44. doi: 10.1007/BF00710605.
About 50 copies of a long-range repeat DNA family with a repeat size of roughly 100 kb and with sequence homology to mRNAs are clustered in the G-light band D of chromosome 1 of the house mouse, Mus musculus. We studied amplified versions of the cluster which are found in many wild populations of M. musculus. They are cytogenetically conspicuous as one or two C-band positive homogeneously staining regions (single- and double band HSRs) which increase the mitotic length of chromosome 1. The double band HSR was phylogenetically derived from a single band HSR by a paracentric inversion. In homozygous condition, such HSRs contribute, albeit not as much as expected from their mitotic length, to the synaptonemal complex (SC) length of chromosome 1. In HSR heterozygous animals an elongation of the SCs was not noticeable. In single band HSR heterozygous males, synapsis proceeds regularly and continuously from the distal telomere towards the centromeric end without forming buckles. Thus, the single band HSR has no adverse effect on pairing. The same straight pairing behaviour was found in the majority of double band HSR heterozygous spermatocytes. This shows that extensive nonhomologous pairing can take place in the earliest phase of synapsis. Synapsis was discontinuous, leaving the central part of the bivalent 1 asynapsed, in only 14.3% of double band HSR heterozygous cells. In such cells the chromosome 1 SC is completed at a later stage of meiosis. The delay is presumably an effect of the inversion that includes one HSR band and the segment between the two HSR bands.
小家鼠（Mus musculus）1号染色体的G浅带D区域聚集着约50个拷贝的长程重复DNA家族，其重复片段大小约为100 kb，且与mRNA具有序列同源性。我们研究了小家鼠许多野生种群中该簇的扩增版本。它们在细胞遗传学上很显眼，表现为一个或两个C带阳性均匀染色区（单带和双带均一染色区，HSRs），这增加了1号染色体的有丝分裂长度。双带均一染色区是通过臂内倒位从单带均一染色区进化而来的。在纯合状态下，这些均一染色区尽管对1号染色体联会复合体（SC）长度的贡献不如从其有丝分裂长度预期的那么大，但仍有一定作用。在均一染色区杂合动物中，未观察到联会复合体的延长。在单带均一染色区杂合雄性中，联会从远端端粒向着丝粒端正常且连续地进行，不形成扣结。因此单带均一染色区对配对没有不利影响。在大多数双带均一染色区杂合精母细胞中也发现了相同的直接配对行为。这表明在联会的最早阶段可以发生广泛的非同源配对。在仅14.3%的双带均一染色区杂合细胞中，联会是不连续的，使得二价体1的中央部分未联会。在这些细胞中，1号染色体的联会复合体在减数分裂后期完成。这种延迟可能是由于包含一个均一染色区带和两个均一染色区带之间片段的倒位所致。
