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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The relative number of ribosomal RNA genes of the acrocentric chromosomes in one individual was measured by counting grains after in situ hybridization of 3H-labeled human 18S rDNA to fixed metaphase chromosomes. The relative amount of ribosomal RNA gene activity of each of the same chromosomes was estimated by determining the frequency with which the chromosome's nucleolus organizer region (NOR) was silver stained, the size of the silver-stained region, and how often the chromosome was found in satellite association. Results were similar in phytohemagglutinin-stimulated T-lymphocytes, Epstein-Barr virus transformed lymphoblasts, and fibroblasts. One chromosome 21 had few gene copies and low activity. One chromosome 22 had many gene copies but low activity. Both chromosomes 14 had few gene copies but high activity. The level of expression that can be achieved by rRNA gene clusters can, therefore, be determined by factors other than the number of gene copies.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1076
    Keywords: Duchenne muscular dystrophy, Becker muscular dystrophy ; Carrier diagnosis ; Prenatal diagnosis ; X-linked muscular dystrophies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The indirect approach to carrier detection and prenatal diagnosis of Duchenne and Becker muscular dystrophies based on the study of DNA polymorphisms closely linked to this gene has been followed by five Italian laboratories in the study of 106 pedigrees. Out of 354 women studied up to 1 May 1987, 147 were identified as carriers because of pedigree information and/or of increased creatine phosphokinase (CPK) values. Of the remaining 207, 184 could be assigned to three arbitrarily defined risk categories (low, intermediate and high) using linkage analysis. This disaggregation of women at risk is clearly more useful than that defined before DNA analysis, in which the same 184 women could be assigned only to the low or intermediate risk categories. Prenatal diagnosis was theoretically possible in 90% of carrier women, and was actually performed in 14 pregnancies, which led to the identification of four affected male foetuses, one also having Down syndrome.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The previously unassigned gene coding for the anticoagulatory protein C has been mapped on chromosome 2 using a cDNA probe and genomic blots from a human-hamster somatic cell hybrid panel. The assignments of the genes coding for the coagulation factor X to chromosome 13, and for α1-acid glycoprotein to chromosome 9 have been confirmed using a similar direct approach.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary rRNA gene activity was evaluated by cytologic methods in cultured human cells from two different tissues grown under controlled experimental conditions. The modal and average numbers of silver positive nucleolus organizers (NOs) per cell as well as the distribution of cells with different numbers of silver positive NOs and different combinations of D-plus G-group silver stained chromosomes, were evaluated. Statistically significant differences in the average number of silver positive NOs per cell between leukocytes and fibroblasts grown under standard experimental conditions have been demonstrated. The observed differences became sharper in cells cultured under more restrictive conditions. Also, differences in the frequency of silver positivity of specific chromosomal NOs located on individually indentified chromosomes were observed in cells from the same tissue. Furthermore, differences in the frequency of activation of rDNA clusters located on the same chromosome were also observed between cells from the two tissues. The possible biologic meanings of these findings are discussed.
    Type of Medium: Electronic Resource
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