Heterochromatin, synaptonemal complex, and NOR activity in the somatic and germ cells of a male domestic dog, <i>Canis familiaris</i>(Mammalia, Canidae)

Abstract

C-banding and silver staining of the somatic and germ cells of the male domestic dog, Canis familiaris, have shown that: (1) the amount of C-banding is small compared to most other mammalian species, (2) three pairs of autosomes have nucleolus organizer regions (NORs) at the terminal ends of their long arms, whereas the Y chromosome has an NOR on the terminal end of the short arm, (3) the organization of the synaptonemal complex (SC) is similar to that of other mammalian species, (4) a distinct SC is formed between the long arm of the Y chromosome and probably the short arm of the X chromosome, and (5) the differential axes of both sex chromosomes do not demonstrate fusiform thickenings nor do they stain darkly with silver as do the XY bivalents in many other mammalian species.

Telomeric association: another characteristic of cancer chromosomes?

“…Telomeric associations have, however, been observed between normal chromosomes with terminally located nucleolus organizers (Pathak et al, 1982;Maia et al, 1987). With the renewed interest in mammalian and human cytogenetics, a number of individual chromosome features not described earlier have recently been reported in human syndromes and cancer cells.…”

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

“…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 value ranged from 4 [6,11,12]. Other reports based on silver staining suggested, however, a higher number of chromosome pairs bearing NORs [1,5,14].…”

NOR association in Canis familiaris

“…Peripheral blood samples from 3 female dogs were cultured and processed for RBG-band induction as previously described (Ronne 1985;Poulsen et al, in press). Ag-NOR staining was modified after Howell and Black (1980) (Kopp et al, 1982a, b;Pathak et al, 1982;Howard-Peebles and Howell, 1983). Since the dog karyotype is not standardized, the reported positions of NORs on dog chromosomes were inconsistent.…”

“…Using high-resolution RBG-banding (Poulsen et al, in press), NORs on 8 different autosomes were observed (fig 1). In males, Pathak et al (1982) and Kopp et al (1982b) figure 3. Translocations in normal dog (Larsen et al, 1978(Larsen et al, , 1979Mayr et al, 1986;Ma and …”

“…However, a G-banded karyotype of Canis lupus (Wayne et al, 1987), which is supported to be homologue to that of Canis familiaris, displayed detailed information about banding patterns and served as a guideline for the numbering system used in the RBG-banded karyotype (Poulsen et al, in press) and in the present study. Several authors have reported on the nucleolar organizer regions (NORs) and NOR associations in the karyotype of the domestic dog (Kopp et al, 1982a, b;Pathak et al, 1982). In this paper, the frequencies of NOR associations and the localization of NORs in the female karyotype of Canis familiaris are presented using sequential RBG-banding and the silver (Ag)-NOR staining technique.…”