MEIOSIS IN AUTOPOLYPLOID CREPIS CAPILLARIS .2. AUTOTETRAPLOIDS
MEIOSIS IN AUTOPOLYPLOID CREPIS CAPILLARIS .2. AUTOTETRAPLOIDS
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DOI：
10.1139/g94-069
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发表时间：
1994-06-01
期刊：
影响因子：
3.1
通讯作者：
VINCENT, JE
中科院分区：
文献类型：
--
作者：
JONES, GH;VINCENT, JE
用电镜观察了同源四倍体Crepis capillaris的减数分裂染色体配对，并与光镜观察的中期染色体构型进行了比较。在所有三个四体中，前期I四价体的频率都很高。（A，D和C），部分取决于染色体大小。在中期I，四价体频率低得多，并且强烈依赖于染色体大小。有没有证据表明，多价消除在前期我在这个系统中，在中期我的多价频率的减少可以解释为适当放置的交叉不足。高频率的前期I quadrivalents远远超过三分之二的预期在一个简单的模型与两个终端独立的配对起始位点每四体，这表明多个配对起始发生。直接观察显示相对较高的频率配对伙伴开关（PPS）在前期I，这证实了这一建议。每个四体的PPS的数量显示出很好的拟合泊松分布，其位置分布沿着染色体是随机的和非本地化的。这些观察有利于配对启动模型的基础上，大量的均匀分布的自主配对网站，每个统一的和低概率产生的PPS。
Meiotic chromosome pairing of autotetraploid Crepis capillaris was analysed by electron microscopy of surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I chromosome configurations. Prophase I quadrivalent frequencies are high in all three tetrasomes. (A, D, and C) and partially dependent on chromosome size. At metaphase I quadrivalent frequencies are much lower and strongly dependent on chromosome size. There is no evidence for multivalent elimination during prophase I in this system, and the reduction in multivalent frequency at metaphase I can be explained by an insufficiency of appropriately placed chiasmata. The high frequencies of prophase I quadrivalents far exceed the two-thirds expected on a simple model with two terminal independent pairing initiation sites per tetrasome, suggesting that multiple pairing initiation occurs. Direct observations reveal relatively high frequencies of pairing partner switches (PPSs) at prophase I, which confirms this suggestion. The numbers of PPSs per tetrasome show a good fit to the Poisson distribution, and their positional distribution along chromosomes is random and nonlocalized. These observations favour a model of pairing initiation based on a large number of evenly distributed autonomous pairing sites each with a uniform and low probability of generating a PPS.