ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract We examined the three-dimensional arrangement of bivalents and, in particular, a chain of four chromosomes (chain quadrivalent) in the metaphase I spindle of pollen mother cells ofAllium triquetrum by confocal microscopy. Firstly, we show by optical sectioning and three-dimensional image reconstruction that the cooriented pairs of centromeres of all seven bivalents lie virtually parallel to each other in the metaphase I spindle, parallel to the long axis of the spindle. Secondly, we like-wise show that the four centromeres of the chain quadrivalent are aligned in the metaphase I spindle in, essentially, atwo-dimensional array, not in a three-dimensional array, as proposed by some other authors. This two-dimensionality has its basis, we argue, in the principle that poleward directed spindle forces minimise centromere-to-pole distances and therefore align pairs of centromeres connected to opposite poles most axially (vertically) in the spindle. These distances are minimised for the quadrivalent as a whole only when it lies in two dimensions, i.e. in aplane parallel to the spindle axis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00650900
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