ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Microdissection studies of the dividing neuroblast of the grasshopper,Chortophaga viridifasciata, lead to the following conclusions: 1. The spindle at metaphase is a semisolid body situated in a fluid cytoplasm; it consists largely of longitudinally oriented components; it appears to be attached at its poles to the adjacent region of the plasma membrane by weak astral fibers. From prometaphase through early anaphase the chromosomes are securely attached to the spindle at their centromeres. The spindle develops during prometaphase from the fluid karyolymph; during anaphase it undergoes liquefaction, which begins in the equatorial region and spreads poleward with or slightly in advance of the chromosome centromeres. By late anaphase the chromosomes at each pole are held firmly in a circle at their proximal ends. 2. The interzonal region of the anaphase cell consists of fluid protoplasm traversed by fine, invisible interzonal connections joining the distal ends of sister chromosomes. Its elongation during anaphase is an intrinsic process that is independent of any attachment of the spindle to the adjacent cell membrane by astral rays and appears to be responsible for much of the anaphase separation of sister chromatids. 3. Early anaphase separation of sister chromatids begins at the centromere and progresses distally. 4. Polarization of the neuroblast is largely independent of the spindle and chromosomes. 5. Formation of the cleavage furrow is independent of the spindle and chromosomes, but its position depends to a limited extent on their position at late anaphase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01271487
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