Document Detail

The role of chromosomal proteins in the C-banding of Allium cepa chromosomes.
MedLine Citation:
PMID:  89024     Owner:  NLM     Status:  MEDLINE    
When chromosomes of Allium cepa are subjected to a C-banding procedure (incubation in saturated barium hydroxide followed by phosphate buffer at 60 degrees C for 1 h) and then treated with Giemsa stain, bands appear at the telomeres of all chromosomes. Microspectrophotometric measurements of Feulgen-DNA content, demonstrated that the C-banding procedure extracted DNA from the nuclei. Staining of banded chromosomes with several DNA-specific stains showed that this loss was differential, with the band DNA exhibiting more resistance to extraction than that of the rest of the chromosome. The C-banding procedure did not extract chromosomal proteins, however, and no difference in mass per unit length could be detected by Nomarski optics between band and interband regions. Several experiments demonstrated that chromosomal proteins play a significant role in C-banding. First, treatment of chromosomes with pronase before C-banding resulted in the elimination of differential staining with Giemsa. Furthermore, in preparations where the DNA was completely hydrolysed with hot TCA, the remaining chromosomal proteins were found to exhibit a differential affinity for Giemsa stain. Amido black staining demonstrated that total chromosomal protein was uniformly distributed after the hot TCA digestion, but the proteins localized in the telomeres had a greater affinity for the Giemsa stain than the bulk of the chromosomal proteins. When the TCA-digested chromosomes were subjected to the C-banding procedure before staining, the differential affinity of the telomeres for the Giemsa stain was lost. Thus, C-banding appears to be the result of a complex interaction between protein and DNA in which the greater resistance to extraction of the band DNA is necessary to stabilize and preserve chromatin protein which exhibits a differential affinity for Giemsa stain.
S M Gendel; D E Fosket
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Cytobios     Volume:  22     ISSN:  0011-4529     ISO Abbreviation:  Cytobios     Publication Date:  1978  
Date Detail:
Created Date:  1979-10-17     Completed Date:  1979-10-17     Revised Date:  2000-12-18    
Medline Journal Info:
Nlm Unique ID:  0207227     Medline TA:  Cytobios     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  155-68     Citation Subset:  IM    
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MeSH Terms
Chromosome Banding*
Chromosomes / ultrastructure*
DNA* / analysis
Nucleoproteins / physiology*
Plants / ultrastructure*
Pronase / pharmacology
Staining and Labeling
Reg. No./Substance:
0/Nucleoproteins; 9007-49-2/DNA; EC 3.4.24.-/Pronase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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