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Cell structure - Nucleus - Preparation of chromosomes
Preparation of chromosomes
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| Description |
To investigate chromosomes, lymphocytes are particularly appropriate. They are obtained from heparinized blood or from amniotic fluid for investigations on embryos and foetuses.
The individual shape of the chromosomes can only be seen in the mitotic phase of the cells: in prophase the chromatin condenses, the chromosomes become visible. The sample, in this case blood, is added to the culture medium. This contains phytohemagglutinin to stimulate the mitotic activity of white blood cells.
After 3 days of culturing, the cells have multiplied sufficiently. By adding the alkaloid colcemid, the microtubules, which form the mitotic spindle, are destroyed. Thus progress of mitosis is interrupted; the mitoses accumulate.
After centrifuging off the cell suspension, the sediment is allowed to swell up in hypotonic potassium chloride solution.
After 10 minutes the supernatant solution is decanted and the sediment fixed with methanolic glacial acetic acid. On evaporation of the fixative solution the chromosomes stretch out.
This stretching is termed spreading. In cases of too intensive spreading the associated chromosomes lie far apart; in cases of insufficient spreading, they overlap and are then difficult to identify. After trypsin treatment the preparation is stained with Giemsa stain and can be examined.
Duration: 02:13 min
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Sources
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1. Mitosis; Karyokinesis and Cytokinesis in Animal and Plant Cells. BEREITER-HAHN, JÜRGEN, Frankfurt a. M. and FALK, HEINZ, FREIBURG I. BR. Publ.: 1977. IWF, Göttingen: C 1257.
2. Spreading of chromosomes. CLAUSSEN, UWE, Jena.
3. Stained chromosomes. BEREITER-HAHN, JÜRGEN, Frankfurt a. M.
4. BEREITER-HAHN, JÜRGEN; PETERS, WINFRIED S.: Nucleus of Life - From Gene to Protein. CD-ROM C 7103. MMcD, Düsseldorf; interActive Systems iAS, Marburg, Berlin; IWF, Göttingen, 2003.
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Abbreviations
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Order |
This film is part of the CD-ROM Nucleus of Life - From Genes to Proteins. You can order it at the IWF Knowledge and Media gGmbH.
Also available as clip.
Order no.:
C 13112
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