Ag-NOR Banding Research Articles

A 9p13→p24 duplication coupled with a whole 22q translocation onto 9p24

We report on a 3-year-old girl with a typical 9p trisomy syndrome, whose 45-chromosome karyotype includes a 9p+. As assessed by G, C and Ag-NOR bands, the rearranged chromosome resulted from a 9p13-->p24 direct duplication coupled with a translocation of the whole 22q onto 9pter, had heterochromatin at the junction site, lacked both nucleolar organizing regions (NORs) and centromere dots at the unconstricted fusion point, and was present in all metaphases scored. FISH results: a 9p subtelomere probe gave a diminished signal on the 9p+ precisely at the duplication junction 9p24::9p13, but no labeling was observed at the 9;22 translocation site; a pancentromeric alphoid probe labeled all centromeres, and gave a distinct signal at the 9pter;22cen junction. Hence, her karyotype was 45,XX,rea(9;22)(9qter-->9p24::9p13-->9p24::22p10-->22qter).ish rea(9;22) (9psubtel+dim,pancen+). Parental chromosomes were normal. The distinctiveness of the present centromere-telomere fusion rests on the coupling of an intrachromosomal distal duplication with a whole-arm translocation including alphoid DNA onto the duplicated segment. The centromeric inertia of the residual alphoid DNA in the present case compares with the variable functional status of the chromosome 22 centromere in true heterodicentrics involving such a chromosome.

Cytogenetic Analysis of eight Lily Genotypes

Abstract Chromosomal banding markers were established for four lily species - L. candidum, L. × formolongi, L. henryi, L. pumilum and four belonging to horticultural group Oriental hybrids - cultivars - Alma Ata’, ‘Expression’, ‘Marco Polo’ and ‘Muscadet’. Banding markers were provided by Ag-NOR, CMA3/DA/DAPI and C-Giemsa stain-ings. These techniques enabled to establish markers for identification from 4 to 17 out of 24 chromosomes depending on genotype and technique. Negative DAPI bands were not always observed whereas Ag-NOR and CMA3 bands were distinctly visible on chromosomes and co-localized the positions of secondary constrictions which enabled to distinguish primary from secondary constrictions, even if these structures were localized close to each other. Additional CMA3 bands were present intercalary on chromosomes. The C banding method revealed the most markers for chromosomes identification but the technique was difficult to standardisation and results were not fully reproducible. For each genot...

Karyotype, DNA Content and Meiotic Behaviour in Five South American Species ofVicia(Fabaceae)

This paper presents the karyotype, DNA content and meiotic behaviour of five species ofViciafrom Argentina (V. macrogramineaBurk.,V. gramineaSM.,V. epetiolarisBurk.,V. pampicolaBurk. andV. nanaVog.). All the species have the same chromosome number and karyotype formula (2n=14; 6m+4st+4t). Each species, however, displays a characteristic number and position of the nucleolar organizer region (NOR) and different sizes of the respective satellites, confirmed by Ag-NOR banding. Moreover, significant differences were found in the total chromosome volume (TCV) and DNA content of the species. Positive correlations between DNA content and TCV, and between DNA content and type of life cycle were also found. TCV and DNA content are lower inV. nana(annual) and higher inV. macrograminea(biennial–perennial). The material displayed marked karyotypic orthoselection, with similar karyotypes in all studied species, even when the overall chromosome size varied. Evolutionary changes in DNA amount are proportional to the relative length of each chromosome arm, maintaining karyotypic uniformity. Significant differences were found between the meiotic behaviour ofV. gramineaand that of the other species.V. gramineahas a lower frequency of ring bivalents and chiasmata per cell, and also has a lower interstitial chiasma frequency. In general, the results are congruent with the morphological data reported for these species.

Behavior of NOR-Bearing Telosomes in Japanese Garden Iris (Iris ensata Thunb.).

The behavior of NOR-bearing telosomes in the telotrisomic and its telocentric progenies of Iris ensata was examined by a silver-staining method. In the cross of the telotrisomic “Telotri-1” × the diploid cultivar “Shishinden”, the female transmission rate of a telosome was 15. 6%. All the telotrisomics except one (Telotri-1-1) had 4 NOR-bearing chromosomes and a telosome with 2 Ag-NOR bands which were observed in the maternal plant “Telotri-1”, and a telosome with 2 Ag-NOR bands in the monotelodisomic “Monotelodi-1” was also transmitted from the maternal one. On the contrary, the telotrisomic “Telotri-1-1” had 5 NOR-bearing chromosomes and a telosome with 1 Ag-NOR band. The appearance of this telosome provided the conclusive proof that a simple translocation of 1 Ag-NOR band of the telosome with 2 Ag-NOR ones to a non NOR-bearing chromosome took place in “Telotri-1”. Such a structural change of the telosome was recognized in 9.1% of the telocentric progenies of “Telotri-1”.

Karyotype differentiation between two species of carangid fishes, genusTrachurus (Perciformes: Carangidae)

A karyological study ofTrachurus trachurus andT. mediterraneus (Perciformes: Carangidae) was conducted by standard, fluorochrome staining (CMA3, mithramycin, quinacrine mustard, DAPI), C-, Ag-NOR, and Alu-I banding methods. The karyotypes of both species consisted of 2n = 48 chromosomes, but of different FN:T. trachurus possessed a chromosome complement of 2 metacentric and 46 acrocentric elements, fundamental number (FN) = 50 andT. mediterraneus, a chromosome complement of 4 metacentric, 4 submetacentric, 14 subtelocentric and 26 acrocentric chromosomes, FN = 70. In neither of the two taxa investigated were heteromorphic sex chromosomes observed. The nucleolar organizer region was interstitially located on the long arm of the Ist pair of chromosomes in both species, intermediate inT. mediterraneus and subterminal inT. trachurus. Constitutive heterochromatin was found in nearly all centromeric and telomeric regions inT. trachurus; inT. mediterraneus it formed less intense telomeric and centromeric bands and thin interstitial bands on eight chromosome pairs. In addition, the C-positive material reacted differently to the digestion with endonuclease Alu-l in the two species. The results are discussed and compared with karyological data known for other species of Carangidae.

Chromosome complement, C-banding, Ag-NOR and replication banding in the zebrafish Danio rerio.

The chromosome complement of Danio rerio was investigated by Giemsa staining and C-banding, Ag-NORs and replication banding. The diploid number of this species is 2n = 50 and the arm number (NF) = 100. Constitutive heterochromatin was located at the centromeric position of all chromosome pairs. Nucleolus organizer regions appeared in the terminal position of the long arms of chromosomes 1, 2 and 8. Replication banding pattern allowed the identification of each chromosome pair.

Correspondence between C-banding and Ag-NOR in the Sex Chromosomes of Belostoma oxyurum (Belostomatidae, Heteroptera).

The mitotic and meiotic sex chromosomes of Belostoma oxyurum have been analyzed by C-banding and Ag-NOR staining. In mitotic prometaphases the Y chromosome and both telomeric regions of the X are C positive. However, at meiosis one telomeric region of the X chromosome presents always a C positive band, while the other telomeric region of this chromosome and the whole of the Y chromosome are light C banded during diplotene, the diffuse stage and early diakinesis. All these bands appear C positive by late diakinesis. In mitotic prometaphases, a positive Ag-NOR is revealed at one telomeric region of the X chromosome, but not in the Y chromosome. Besides, some intra and/or interindividual variation in NOR expression in the X chromosome is encountered. No positive Ag-NOR band is observed at meiosis.A comparison of the results obtained in mitotic and meiotic cells after C- and Ag-NOR banding lead to the conclusion that in Belostoma oxyurum the intermediate staining of the C-bands of the sex chromosomes at meiosis is related to both the DNA composition (repetitive DNA, rRNA genes) and its packaging (cycle of condensation).

Prometaphase chromosomes of the howler monkey (Aloutta caraya): G, C, NOR, and restriction enzyme (RES) banding.

Prometaphase lymphocyte chromosomes from eight adult argentinian Alouatta caraya females were characterized using sequential G-C banding techniques, Ag-NOR bands and bands obtained with the restriction enzymes Hae III, Eco RI, Alu I and Sau 3A. The cytogenetic analysis showed 2n = 52, with four, five, or six NOR chromosomes. Digestion with Hae III and Eco RI produced G-like-bands. Centromere regions and two interstitial C-bands (in chromosomes number 16 and 21) showed intraindividual or interindividual heterochromatic polymorphisms. Alu I digestion produced C-like bands with gaps in the centromere regions, and Sau 3A produced C-like bands. The karyotypes and banding patterns of A. caraya, A. palliata, A. belzebul, and A. seniculus are compared, based on whole chromosome and whole arm homeologies. © 1994 Wiley-Liss, Inc.

Karyotype, C-banding, and Ag-NOR analysis in Diplodus bellottii (Sparidae, Perciforms). Intra-individual polymorphism involving heterochromatic regions

A karyotype analysis was carried out in nine specimens of the Sparid species Diplodus bellottii using conventional staining, as well as C-banding and Ag-NOR banding techniques, showing, respectively, 2n = 46 and fundamental number (FN) = 54, and scarce heterochromatic areas irregularly distributed and up to four NOR active regions that were C positive. When compared with the karyotypes of other related species, one centric fusion giving rise to a large metacentric pair and several pericentric inversions seem to have been involved in the karyotype evolution. An intra-individual polymorphism was detected in one specimen, resulting in two karyotypic forms in roughly identical proportion, owing to a larger C-band by the NOR regions, appearing either in a terminal position of the short arms of pair 2 or in telomeric position of pair 3. These findings suggest that the extra heterochromatic segment responsible for the heteromorphism apparently only involves associated heterochromatin and not the NORs themselves. This C-positive block seems to have eventually been transferred between heterologous NOR chromosomes by a somatic event, facilitated by the physical proximity of NOR pairs in the nucleolus.

Chromosome banding studies of the osprey Pandion haliaetus (Aves, Falconiformes)

The karyotype of the osprey Pandion haliaetus was studied using GTG, CBG, and NOR banding techniques on fibroblast cells derived from skin tissue cultures. Autosome pairs 1–25, Z, and W were identified by their GTG banding patterns. The remaining 11 pairs could not be identified individually because of their similarity and small size. CBG bands were restricted to the centromere region of each chromosome, including the W chromosome, which did not show an extensive C-positive region typical of most birds. Silver NOR banding revealed the presence of a nucleolar organizing region on chromosome 2 located at the secondary constriction near the proximal end of the long arm. The position of this nucleolar organizing region appears unique among Aves and may serve as a marker for tracing the phylogenetic origin of this monotypic family. No clear relationship to other Falconiformes was evident in the karyotype, although similarities to Accipitridae were found.Key words: osprey, Pandion haliaetus, karyotype, GTG bands, CBG bands, Ag-NOR bands.

A Comparison of Karyotype, Ag-NOR Bands and DNA Content in Amaryllis and Hippeastrum (Amaryllidaceae)

This paper presents new data useful in the consideration of the relationships between Amaryllis belladonna L., type species of the monotypic South African genus, and species of the South American genus Hippeastrum Herb. A. belladonna (2n = 22) has a karyotype comprising 4 pairs m + 1 pair m-sm + 6 pairs sm chromosomes; the m pairs are shorter than the other ones. The pair m-sm has a terminal satellite on the short arm; the secondary constriction proximal to this is a nucleolar organizer, as demonstrated by Ag-NOR banding. The constant basic karyotype in Hippeastrum (x = 11) is more asymmetrical and comprises 4 m + 4 sm + 3 st; the m are shorter than the others. One st chromosome has a terminal nucleolar organizer (NOR) secondary constriction on the short arm. Furthermore, the karyotype is also more asymmetrical because it has more variation of chromosome total length. The DNA content in A. belladonna is 2C = 38.29 pg while in diploid species of Hippeastrum studied, it ranges from 26.90 pg to 34.18 pg, being represented in this paper by H. parodii with 2C = 29.93 pg. These results indicate that important chromosome differences exist between South African and South American taxa. These differences are supported by morphological and anatomical studies reported by other authors.

Marker chromosomes in parents to children with Down's syndrome

The incidence of an extra marker chromosome in the normal population is low, about 0.26 per 1,000, and that of trisomy 21 is about 1.25 per 1,000. The incidence of both these chromosomal abnormalities in the same family should be very low, if this occurs by chance. Thirteen cases of Down's syndrome in 10 families in which one of the parents had an extra marker chromosome have been reported earlier. In three of these families there were two siblings with Down's syndrome. The present report describes two families in which an extra marker chromosome was found in one of the parents and in which three of the offspring had a trisomy 21 karyotype. From the findings at Q- and AgNOR banding of the chromosomes it seemed probable that in one case this extra marker chromosome was an isochromosome for the short arm of an acrocentric chromosome. It seems very likely that marker chromosomes in healthy mothers are of pathogenetic importance for non-disjunction, resulting in a trisomy 21 offspring. A finding of an extra marker chromosome in one of the parents should therefore be taken into consideration in genetic counselling.

A spontaneous clone of Fanconi anemia fibroblasts with chromosome abnormalities and increased growth potential.

In a diploid fibroblast culture from a patient with Fanconi anemia (FA), we observed the evolution of a chromosomally abnormal clone that had an unusual proliferative advantage and increased growth potential compared with the diploid FA cells. Q-, G-, C-, and Ag-NOR banding analyses revealed that the clonal cells had a chromosomal complement 46,XY, -5, -21, +mar1, +mar2, and were trisomic for a segment of the long arm of chromosome 5 and most of the long arm of No. 21. The retention of chromosome instability in the clonal cells indicates that the alteration in growth characteristics did not result from a mutation to the wild-type allele at the FA locus.