Orientation and segregation of a micromanipulated multivalent: familiar principles, divergent outcomes.
Orientation and segregation of a micromanipulated multivalent: familiar principles, divergent outcomes.
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显微操作多价体的定向和分离：熟悉的原理，不同的结果。
DOI：
10.1007/bf00582834
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发表时间：
1992
期刊：
影响因子：
1.6
通讯作者：
Nicklas,RB
中科院分区：
文献类型：
--
作者：
Arana,P;Nicklas,RB
我们研究了一种特定的四价体在活的蝗虫精母细胞中的定位和分离。通过显微操作将四价体从主轴上分离出来，然后根据需要放置和弯曲。分离的四价体在主轴上重新连接和定向。它们的取向是由在有丝分裂和减数分裂中适用于普通染色体的相同原理决定的，但结果不同。四价染色体的某些特征导致了不同的取向，而不是普通染色体典型的单一取向。四价体中的两个动点通过异常长而灵活的染色体臂连接在一起。这些动线可能朝向相同的极点或相反的极点，并且倾向于最初朝向它们朝向的极点。因此，灵活连接的运动中心的初始方向是可变的，而且它们经常重新定向。相比之下，另外两个动点就像那些小的二价体一样紧密相连，因此表现出典型的背靠背排列。通常，这种排列很快会导致两个动点稳定地指向相反的两极。然而，有时背靠背的排列改变为并排排列，从而有利于两个运动中心指向同一极点。这种不同行为的综合影响是，四价体有四个稳定的取向，每个取向导致后期染色体的不同分布。结果就是基因混乱。具有讽刺意味的是，这种混乱是由相同的机制产生的，在普通的二价体和有丝分裂染色体中，产生单一稳定的方向和遗传上合适的染色体分布。
We studied the orientation and segregation of a particular quadrivalent in living grasshopper spermatocytes. Quadrivalents were detached from the spindle by micromanipulation, then placed and bent as desired. The detached quadrivalents reattach and orient on the spindle. Their orientation is determined by the same principles that apply to ordinary chromosomes in mitosis and meiosis, but the outcome is different. Certain characteristics of the quadrivalent lead to a variety of orientations rather than the single one typical of ordinary chromosomes. Two kinetochores in the quadrivalent are linked to the others by unusually long, flexible chromosome arms. These kinetochores may face either the same pole or opposite poles and tend to orient initially to the pole toward which they face. Consequently, the initial orientation of the flexibly linked kinetochores is variable, and, moreover, they frequently reorient. In contrast, the other two kinetochores are as rigidly connected as those in a small bivalent and so display the typical back-to-back arrangement. Usually, this arrangement leads quickly to a stable orientation of the two kinetochores to opposite poles. Sometimes, however, the back-to-back arrangement changes to a side-by-side arrangement so that the orientation of both kinetochores to the same pole is favored. The combined effect of this diverse behavior is that the quadrivalent has four stable orientations, each leading to a different distribution of chromosomes in anaphase. The result is genetic chaos. Ironically, this chaos is produced by the same mechanisms that, in ordinary bivalents and mitotic chromosomes, produce a single stable orientation and genetically appropriate chromosome distribution.