15 research outputs found
Chromosomal location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela)
No full textThe 5S ribosomal RNA genes have been localized in mitotic and lampbrush chromosomes of Triturus vulgaris meridionalis by in situ hybridization. These genes are clustered in a single locus in an intercalary position of the long arm of chromosome XI. In lampbrush chromosome XI the 5S genes are located near a loop landmark mapped at 66 units
Chromosome location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela). II. Intraspecific variability in number and position of the chromosome loci for 18S + 28S ribosomal RNA.
No full textChromosome location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela).IV. Comparison between in situ hybridization with H3 18S+28S rRNA and AS-SAT staining
No full textChromosome location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela)
No full textThe mitotic chromosomes of six specimens from Triturus vulgaris meridionalis have been examined by both in situ hybridization with 3H 18S + 28S rRNA and AS-SAT staining method. The results of these two sets of experiments can be summarized as follows: 1) in each specimen the NORs and the additional ribosomal sites, which react positively to in situ hybridization with 3H 18S + 28S rRNA, are also stained by silver; 2) other chromosomal regions, which do not hybridize in situ with 3H 18S + 28S rRNA, are on the other hand stained by the AS-SAT method. These latter AG-positive sites show a species-specific pattern of chromosomal distribution
Chromosome location of the ribosomal genes in Triturus vulgaris meridionalis (Amphibia Urodela). III. Inheritance of the chromosomal sites for 18S + 28S ribosomal RNA.
No full textIn Triturus vulgaris meridionalis, the 18S + 28S rDNA sequences have been shown to be located in a number of additional chromosomal sites besides the nucleolus organizing region. The additional ribosomal sites have been found to vary as to their number and chromosomal location in different individuals of the species.--The data presented in this study concern the chromosomal distribution of the ribosomal sequences as analyzed by in situ hybridization technique in two individuals as well as in their offspring. The evidence obtained by this analysis indicates quite clearly that all 18S + 28S rRNA sites present in each individual genome are inherited according to simple mendelian principles
The ribosomal DNA in Triturus vulgaris meridionalis : are the additional ribosomal genes amplified during oogenesis?
No full textComparison between AS-SAT staining and in situ hybridization in the chromosomes of Triturus vulgaris meridionalis
No full textMolecular organization of ribosomal RNA genes clustered at variable chromosomal sites in Triturus vulgaris meridionalis (Amphibia Urodela)
No full textThe ribosomal RNA genes of Triturus vulgaris meridionalis (Amphibia, Urodela) show the peculiar feature of being clustered not only at the nucleolar organizer, present in the species at a definite chromosome location, but also at "additional ribosomal sites" which are highly variable in number and chromosomal distribution among individuals. The additional ribosomal sites are most often found at specific chromosome regions, such as telomeres, C-bands and centromeres, in virtually all the chromosomes. With increasing numbers of additional clusters, the genomic dosages of ribosomal RNA genes are found to increase over a tenfold range, though not linearly. At a molecular level, the ribosomal DNA repeats differ in size because of discrete variations in the length of the non-transcribed spacers. However, the resulting length heterogeneity of the gene family is rather limited within a single genome as well as within the species. Many of the ribosomal loci appear to be internally homogeneous with respect to the repeat length. Moreover, separate clusters from distant genomic regions can share the same size class of ribosomal repeats even in the same specimen. The nucleolar organizer is mostly endowed with "shorter" ribosomal repeating units, ranging in size from 13.7 X 10(3) to 15.2 X 10(3) base-pairs. The additional ribosomal sites are characterized by the occurrence of "longer" repeats, ranging in size from 16.2 X 10(3) to 19.7 X 10(3) base-pairs. The "shorter" class of ribosomal repeats is always detected in the amplified ribosomal DNA, suggesting that the nucleolar organizer locus is involved in the amplification process in most oocytes. "Longer" ribosomal repeats are also detectable in the amplified ribosomal DNA of a few females
Chromosome location of the genes for 28S, 18S and 5S ribosomal RNA in Triturus marmoratus (Amphibia Urodela)
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