Chromosomal localization and activity of nucleolar organizer regions in the dog (Canis familiaris)

Abstract

Using fluorescent in situ hybridization on Q-banded chromosomes, nucleolar organizer regions (NORs) were localized on canine chromosomes 7qter, 17qter, Yqter and also terminally on a small autosome, not yet included in the dog standard karyotype. The analysis of NOR activity was carried out on Ag-I stained metaphases originating from 27 individuals (10 males and 17 females). The mean number of silver stained NORs was 6.0 in males and 5.3 in females and the modal number was 7 and 6, respectively. Interindividual variability of the mean and modal numbers of silver NORs was observed. The lowest individual mean number of NORs was 4.2 and the highest 7.0, and the modal le plus élevé de 7, la valeur modale se situant entre 4 et 7. © Inra/Elsevier, Paris NOR / chien / hybridation fluorescente in situ / coloration par l'argent

Preliminary investigation on the variation of the nucleolar organizer region in the breeding chinchilla karyotype

“…In humans, it can vary from 5 to 10, with clear individual, breed and population differences (9). Experiments with dogs showed that in the canine genome NORs are most often active on chromosome pairs 8,7,6,9,12, and 10 (the order is based on the degree of transcriptional activity), and least often on pairs 5 and 11 (25). Similar individual differences in the number of rDNA in NOR chromosomes were also observed in pigs (23), mice (33), rats (3), the Cavidae family (11), cattle (30), the Cervidae family (10), and horses (40).…”

Review

“…The following chromosome pairs of these species bear the NORs: 1, 4, 13 and Y in the Chinese raccoon dog (PIENKOWSKA and ZAGALSKA 2001) and 11, 12, 18 and Y in the Japanese raccoon dog (WARD et al 1987). The NORs in the canine karyotype were detected on two large autosomes (7 and 17), one small autosome and on the Y chromosome (MÄKINEN et al 1997;PIENKOWSKA and SWITONSKI 1998). The presence of the NOR on the Y chromosome reflects the evolutionary similarity of this chromosome in the dog and raccoon dog.…”

Canine 5S rRNA: nucleotide sequence and chromosomal assignment of its gene cluster in four canid species

“…Kopp et al, 1982;Howard-Peebles et al, 1983;Mayr et al, 1986) provided inconsistent results about the number and the chromosomal localization of NORs. Recent publications by Mäkinen et al (1997) and Pienkowska and Switonski (1998) both identified three autosome pairs and the Y chromosome carrying the gene cluster for major rRNA genes using FISH and FISH/silver staining, respectively. Besides canine chromosome 7 and 17, a third autosome bearing the locus belonged to the group of small chromosomes (CFA 22-38), which were not yet included in the international standard karyotype.…”