U Ståhle

Lund University, Lund, Skåne, Sweden

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Publications (5)5.59 Total impact

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    ABSTRACT: The total length of the two chromosomes (n = 2) which build the genome of Haplopappus gracilis is about 14.6 microns. A well-defined nucleolus organizer is found in chromosome No. 2. Heterochromatin is seen in interphase nuclei mainly associated with the nucleolus. This heterochromatin is late in replicating as shown by H3-thymidine incorporation. In the analytical ultracentrifuge Model E the DNA of Haplopappus shows a DNA satellite with a buoyant density of 1.699 g/ml corresponding to a guanine-cytosine content of 39.8 %, the corresponding values for the main band being 1.693 g/ml and 36.7 % GC.Hybridization between 28S hamster ribosomal H3-RNA and total Haplopappus DNA fractionated on CsCl gradients reveals that the ribosomal cistrons are present in the DNA satellite. When the fractions — of similar gradients — which contain the ribosomal DNA are collected and their DNA is centrifuged in the analytical ultracentrifuge, the DNA satellite increases appreciably in size. These results lead us to conclude that the ribosomal cistrons are localized in the DNA satellite. Moreover, there is a high level of redundancy of the genes for ribosomal RNA in Haplopappus. Since chromosome No. 2 contains the nucleolus it is suggested that the DNA sequences of this DNA satellite are located in this chromosome.
    Preview · Article · Feb 2009 · Hereditas
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    ABSTRACT: The total length of the two chromosomes (n = 2) which build the genome of Haplopappus gracilis is about 14.6 microns. A well defined nucleolus organizer is found in chromosome No. 2. Heterochromatin is seen in interphase nuclei mainly associated with the nucleolus. This heterochromatin is late in replicating as shown by H3 thymidine incorporation. In the analytical ultracentrifuge Model E the DNA of Haplopappus shows a DNA satellite with a buoyant density of 1.699 g/ml corresponding to a guanine cytosine content of 39.8%, the corresponding values for the main band being 1.693 g/ml and 36.7% GC. Hybridization between 28S hamster ribosomal H3 RNA and total Haplopappus DNA fractionated on CsCl gradients reveals that the ribosomal cistrons are present in the DNA satellite. When the fractions of similar gradients which contain the ribosomal DNA are collected and their DNA is centrifuged in the analytical ultracentrifuge, the DNA satellite increases appreciably in size. These results lead to the conclusion that the ribosomal cistrons are localized in the DNA satellite. Moreover, there is a high level of redundancy of the genes for ribosomal RNA in Haplopappus. Since chromosome No. 2 contains the nucleolus it is suggested that the DNA sequences of this DNA satellite are located in this chromosome.
    No preview · Article · Feb 1975 · Hereditas
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    ABSTRACT: The main band DNA of Phaseolus coccineus has a buoyant density of 1.692 g/ml. In roots, shoots, integuments and suspensors there is a DNA satellite with a buoyant density of 1.700 g/ml. The satellite of the roots, shoots and integuments represents approximately 28.2 %, 29.4 % and 34.7 % respectively of the total DNA. In suspensors, where polyteny occurs, besides the 1.700 g/ml satellite there is a second one at 1.696 g/ml. They represent about 32.9 % and 13.1 % of the total DNA. H3-25S and H3-18S ribosomal RNA of Phaseolus coccineus were hybridized separately with DNA of shoots from CsCl gradient fractions. In both hybridizations the peak of labelling coincides with the position of the DNA satellite with a buoyant density of 1.700 g/ml. Thus the genes for 25S and 18S are mainly located in this DNA component. Hybridization experiments at saturation inputs of H3-25S ribosomal RNA with DNA of shoots, integuments, roots and suspensors give saturation values of 0.72 %, 0.64 %, 0.51 % and 0.42 % respectively. The lower saturation value in the suspensors may indicate an underreplication of ribosomal genes in this tissue. This is partly cancelled out by the amplification in another DNA: that of the second satellite at 1.696 g/ml which does not seem to be part of the ribosomal DNA.
    Full-text · Article · Feb 1975 · Hereditas
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    ABSTRACT: In the cricket Acheta domesticus, the DNA of somatic tissues (heads and legs), centrifuged to equilibrium in CsCl gradients in the Model E ultracentrifuge, shows a DNA satellite with a buoyant density of 1.716 g/ml. This satellite occurs in the same amount (0.8% of the total DNA) and has the same buoyant density as the satellite found in testes. In ovaries (in which most oocytes are at pachytene) the satellite is 5% of the total ovarian DNA and has the same buoyant density. The amount of DNA complementary to ribosomal RNA has been determined using the low temperature formamide hybridization technique and by carrying out separate experiments involving 28S and 18S H 3 RNA of Acheta. The data indicate that the numerical ratio between genes for 28S and 18S rRNA is one, in ovaries, testes and somatic tissues. The degree of amplification found by saturation experiments in the ovaries agrees with the size of the high buoyant density satellite observed in the analytical centrifuge. Under the conditions of personal experiments there were 1,600 rRNA genes per ovarian cell (pachytene) whereas in somatic cells the value obtained was 342 sites. The amount of DNA non homologous to rRNA present in the high buoyant density satellite is approximately 96.3%. This may consist of 'spacer' and other DNA sequences.
    No preview · Article · Feb 1973 · Hereditas

  • No preview · Article · · Hereditas