Visualization of NORs in relation to the precise chromosomal localization of ribosomal RNA genes

Cheung, Sau Wai; Sun, Lei; Featherstone, T.

doi:10.1159/000132731

Cited by 14 publications

(7 citation statements)

References 14 publications

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“…In three animals (Bio 77, Bio 155 and Bio 260) pair 10 showed Ag-NORs on both homologues in the majority of metaphases in two different tissues, while in one specimen (Bio 69) the pattern for the chromosome 10 was predominantly + /-. For the pair 2, the most (CHEUNG et al 1989), but in many cases reflect differences in the level of activity or variability in the number of rDNA genes per NOR, maintained in natural populations as polymorphisms.…”

Section: Resultsmentioning

confidence: 99%

Variability of the nucleolus organizer regions and the presence of the rDNA genes in the supernumerary chromosome ofAkodonaff.arviculoides(Cricetidae, Rodentia)

Yonenaga‐Yassuda

Assis²,

Kasahara

1992

Caryologia

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Section: Resultsmentioning

confidence: 99%

Variability of the nucleolus organizer regions and the presence of the rDNA genes in the supernumerary chromosome ofAkodonaff.arviculoides(Cricetidae, Rodentia)

Yonenaga‐Yassuda

Assis²,

Kasahara

1992

Caryologia

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“…The size and the intensity of the Ag-stained NORs are apparently in a linear relationship with the activity of ribosomal RNA genes from our root cells. The silver-positive chromatin not only corresponds to the locations of rRNA genes (Cheung et al 1989) but is restricted to transcriptionally active DNA (Miller et al 1976;Engel et al 1977;Miller et al 1978;Hofgartner et al 1979).…”

Section: Discussionmentioning

confidence: 99%

Karyotyping Melandrium album, a dioecious plant with heteromorphic sex chromosomes

Ciupercescu¹,

Veuskens²,

Mouras³

et al. 1990

Genome

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and NEGRUTIU, I. 1990. Karyotyping Melandrium album, a dioecious plant with heteromorphic sex chromosomes. Genome, 33: 556-562. Mitotic metaphase chromosomes of Melandrium album obtained from root protoplasts were studied. Morphologically, the chromosomes were either metacentrics or submetacentrics. They were classified into three distinct groups: group A comprising six pairs of autosomal metacentrics, group B comprising five pairs of autosomal submetacentrics, and the sex chromosomes: X and Y. The X chromosome is a metacentric (r = 1.44), which accounts for more than 14% of the genome. The Y chromosome is a metacentric with, virtually, equal arms (r = 1.09) and accounts for 21 % of the genome, being the largest of the complement. The Y:X ratio was 1.4. Ethidium bromide, caffeine, and vinblastine were used to obtain a better resolution and higher frequency of satellited chromosomes 7q and 9p. The proposed karyotype of M. album is 2n = 24, XX, s(7q;9p) for female and 2n = 24, XY, s(7q;9p) for male plants. Nucleolus organizer regions (NORs) were present at the telomeric sites of three chromosome pairs: 7q, 9p, and lop. The NORs were polymorphic, particularly between the nonhomologous chromosomes. The in situ hybridization technique localized the rRNA genes on four chromosome pairs: 5p, 7q, 9p, and lop. The discrepancy between the NORs and the hybridization signals was probably due to the fact that NORs were restricted only to transcriptionally active rRNA genes. It was concluded that for a complete description and characterization of rRNA genes, both NOR detection and in situ hybridization techniques, as cpplementary methods, shouldfie e m p l y d . J I / J Key words: Melandrium album, karyotype, satellites, idiogram, nucleolus organizer regions, in situ hybridization. CIUPERCESCU, D. D., VEUSKENS, J., MOURAS, A., YE, D., BRIQUET, M., et NEGRUTIU, 1. 1990. Karyotyping Melandrium album, a dioecious plant with heteromorphic sex chromosomes. Genome, 33 : 556-562. Les chromosomes en metaphase mitotique de Melandrium album ont ete etudies dans des protoplastes de racines. Morphologiquement, ces chromosomes sont soit metacentriques, soit submetacentriques. 11s ont ete classes en trois groupes distincts : un groupe A comprenant six paires d'autosomes metacentriques, un groupe B constitue de cinq paires d'autosomes submetacentriques, et les chromosomes du sexe X et Y. Le chromosome X est un metacentrique (r = 1,44) representant plus de 14% du genome. Le chromosome Y est metacentrique avec bras virtuellement egaux (r = 1,09); il represente 21010 du genome, etant le plus gros du complement. Le ratio de X:Y est de 1,4. Du bromure d'ethidium, de la cafeine et du vinblastine ont ete utilises pour obtenir une meilleure resolution et une frequence plus elevee des chromosomes 7q et 9p, porteurs de satellites. Le caryotype propose pour le M. album femelle est 2n = 24, XX, s(7q;9p) et, pour le miile, 2n = 24, XY, s(7q;9p). Les regions organisatrices de nucleoles (RONs) ont occupe des sites telomeriques chez trois paires de chromoso...

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“…The size of the silver deposit on the NOR is thought to be positively correlated to the degree of transcriptional activity (HOFGARTNER et al 1979;SCHWARZ-ACHER and WACHTLER 1983;HCJBBELL 1985), although some authors indicate that there is also a relationship between the amount of precipitated silver and the number of rRNA genes (WARBUR- TON and HENDERSON 1979;MARTIN-DELEON 1980;WACHTLER et al 1986;DE CAPOA et al 1988). However, cases have been described in which the size of the Ag-NOR was found to be unproportional to the quantity of rDNA (MILLER et al 1978;BERNSTEIN et al 1981;TANTRAVAHI et al 1981;WACHTLER et al 1986;DE CAPOA et al 1988;CHEUNG et al 1989).…”

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confidence: 99%

Variation in Size of Ag-NORs and Fluorescent rDNA in Situ Hybridization Signals in Six Breeds of Domestic Pig

Mellink¹,

Bosma²,

Haan³

2004

Hereditas

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Variation of the size of silver-stained nucleolar organizer regions (NORs) of chromosomes 10 and 8 was studied in pigs of six breeds (Sus scrofa L.). The silver deposits were quantified by image analysis and the results were normalized for each Ag-NOR chromosome. In general, normalized values for chromosomes 10 were higher than those for chromosomes 8, suggesting that the NOR activity of chromosomes 10 is dominant as compared to that of chromosomes 8. However, high values for chromosomes 8 were found in the Meishan breed and in some Piétrain pigs, indicating a high transcriptional activity of the rRNA genes on these chromosomes. In some pigs, the relative quantities of rDNA in chromosomes 10 and 8 were investigated by fluorescent in situ hybridization and the results were compared with those of the silver staining procedure. It is concluded that Ag-NOR sizes on chromosomes 10 are relatively well correlated to the number of rRNA genes, whereas the absence or the small size of Ag-NORs on chromosomes 8, often observed in pigs, is the result of low NOR activity rather than of absence of rDNA.

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Visualization of NORs in relation to the precise chromosomal localization of ribosomal RNA genes

Cited by 14 publications

References 14 publications

Variability of the nucleolus organizer regions and the presence of the rDNA genes in the supernumerary chromosome ofAkodonaff.arviculoides(Cricetidae, Rodentia)

Variability of the nucleolus organizer regions and the presence of the rDNA genes in the supernumerary chromosome ofAkodonaff.arviculoides(Cricetidae, Rodentia)

Karyotyping Melandrium album, a dioecious plant with heteromorphic sex chromosomes

Variation in Size of Ag-NORs and Fluorescent rDNA in Situ Hybridization Signals in Six Breeds of Domestic Pig

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