Abstract
The distribution of silver-stained nucleolus-organizing regions (NORs) in fibroblast chromosomes from all seven extant species of Equidae are described. There are variations in the number and locations of silver-stained NORs in different species but most of the cells in an individual of any speies had only 2 to 4 silver-stained NORs. In Equus przewalskii and E. caballus NORs were detected on up to three different chromosomes. In E. asinus 11 different chromosomes were observed to possess NOR sites. E. hemionus kulan and E. hemionus onager had NORs on 2 large metacentric pairs and a small acrocentric pair. In E. grevyi and E. burchelli NORs were located on 3 to 4 different pairs. E. zebra hartmannae had silver-staining over the telomere regions of the short arms of the chromosomes 1, 3 and 4. A comparison of G-banded chromosomes and silver-stained NORs has revealed one autosome with conserved G-band patterns and possessing a silver-staining NOR in all the species except E. asinus. Variations in the number and multichromosomal locations of NORs in various species could have evolved by pairing and exchanges between non-homologous chromosomal heterochromatin having similar satellite DNA sequences.
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Arnheim N., Krystal M., Schmickel R., Ryder O. A. & Zimmer F., 1980. Molecular evidence for genetic exchanges among ribosomal genes on non-homologous chromosomes in man and apes. Proc. natn. Acad. Sci. U.S.A. 77: 7323–7327.
Bloom S. E. & Goodpasture C., 1976. An improved technique for selective silver-staining of nucleolus organising regions in human chromosomes. Hum. Genet. 34: 199–206.
Croce C. M., Talavera A., Bascilico C. & Miller O. J., 1977. Suppression of production of mouse 28S ribosomal RNA in mouse-human hybrids segregating mouse chromosomes. Proc. natn. Acad. Sci. U.S.A. 74: 694–697.
Ditties H., Krone W., Bross K., Schmid M. & Vogel W., 1975. Biochemical and cytogenetic studies on the nucleolus organising regions (NOR) of man. Hum. Genet. 26: 47–59.
Ferguson-Smith M. A., 1964. The sites of nucleolus formation in human pachytene chromosomes. Cytogenetics 3: 124.
Goodpasture C. & Bloom S. E., 1975. Visualization of nucleolus organizer regions in mammalian chromosomes using silver staining. Chromosoma 53: 37–50.
Henderson L. M. & Bruere A. N., 1980. Inheritance of Agstainability of nucleolus organizer regions in domestic sheep, Ovis aries. Cytogenet. Cell Genet. 26: 1–16.
Hens L., Kirsch-Volders M., Arrighi F. E. & Susanne C., 1980. Relationship between measured chromosome distribution parameters and Ag-staining of the nucleolus organizer regions. Hum. Genet. 53: 363.
Howell W. M., Denton T. E. & Diamond J., 1975. Differential staining of the satellite regions of human acrocentric chromosomes. Experientia 31: 260–262.
Hsu T. C., Spirito S. E. & Pardue M. L., 1975. Distribution of 18S and 28S ribosomal genes in mammalian genomes. Chromosoma 53: 25–36.
Jackson J. A. & Fink G. R., 1981. Gene conversion between duplicated genetic elements in yeast. Nature 292: 306–311.
Jacobs P. A., Mayers M. & Morton N. E., 1976. Acrocentric chromosome associations in vivo. Am. J. hum. Genet. 28: 567–576.
Klein L. & Petes T. D., 1981. Intrachromosomal gene conversion in yeast. Nature 289: 144–148.
Krystal M., D'Eustachio P., Ruddle F. & Arnheim N., 1981. Human nucleolus organizer of non-homologous chromosomes can share the same ribosomal gene variants. Proc. natn. Acad. Sci. U.S.A. 78: 5744–5748.
Markovic V. D., Worton R. G. & Berg J. M., 1977. Evidence for the inheritance of silver-stained nucleolus organizer regions in the acrocentric chromosomes of man. Hum. Genet. 79: 1–5.
Miller O. J., Miller D. A., Dev V. G., Tantravahi R. & Croce C. M., 1976. Expression of human and suppression of mouse nucleolus organizer activity in mouse-human somatic cell hybrids. Proc. natn. Acad. Sci. USA 73: 4531–4535.
Miller O. J., Berg W. R., Warburton D., Dev V. G. & Miller O. J., 1978. Regulation of rRNA gene expression in a human familial 14p—marker chromosome. Hum. Genet. 43: 289–297.
Miller D. A., Dev V. G., Tantravahi R. & Miller O. J., 1977. Frequency of satellite association of human chromosome is correlated with amount of Ag-staining of nucleolus organizer regions. Am. J. hum. Genet. 29: 490–502.
Nielsen K., Marcus M. & Gropp A., 1979. Localization of NORs in chromosomes of mouse cell lines by a combined 33258-Hoechst and Ag-staining technique. Hereditas 90: 31–37.
Ohno S., Tujillo J. M., Paplan W. D., Kinosita R. & Stenius C., 1961. Nucleolus organizers in the causation of chromosomal anomalies in man. Lancet 2: 128–136.
Pardue M. L. & Hsu T. C., 1975. Locations of 18S and 28S ribosomal genes in the chromosomes of the Indian muntjac. J. Cell Biol. 64: 251–254.
Ryder, O. A., Bowling, A. T., Brisbin, P. C., Carrol, P. M., Gadi, I. K., Hansen, S. K. & Wedemeyer, E., 1983. Genetics of Equus przewalskii Poliakov 1881: Analysis of genetic variability in breeding lines, comparison of equid DNAs, and a brief description of a comparative breeding program in North America. Equus (in press).
Ryder O. A., Epel N. C. & Benirschke K., 1978. Chromosome banding studies in the Equidae. Cytogenet. Cell Genet. 20: 323–350.
Ryder O. A. & Hansen S. K., 1979. Molecular cytogenetics of the Equidae I. Purification and cytological localization of a (G+C)-rich satellite DNA from Equus przewalskii. Chromosoma 72: 115–129.
Schmiday H., Munke M. & Sperling K. 1979. Ag-staining of nucleolus organizer regions on human condensed chromosomes from cells with different ribosomal RNA gene activity. Expl Cell Res. 121: 425–428.
Slighton J. L., Blechl A. E. & Smithies O., 1980. Human fetal 116–1 and 116–2 genes: complete nucleotide sequences suggest that DNA can be exchanged between these duplicated genes. Cell 21: 627–638.
Warburton D., Atwood K. C. & Henderson A. S., 1976. Variation in the number of genes rDNA among human acrocentric chromosomes: Correlation with frequency of satellite association. Cytogenet. Cell Genet. 17: 221–230.
Warburton D. & Henderson A. S., 1979. Sequential silver staining and hybridization in situ on nucleolus organizing regions in human cells. Cytogenet. Cell Genet. 24: 168–175.
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Gadi, I.K., Ryder, O.A. Distribution of silver-stained nucleolus-organizing regions in the chromosomes of the Equidae. Genetica 62, 109–116 (1983). https://doi.org/10.1007/BF00116632
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DOI: https://doi.org/10.1007/BF00116632