Interstitial Bands Research Articles

Distribution of a 375 bp repeat sequence inAllium (Alliaceae) as revealed by FISH

Information about evolutionary relationships between species of the genusAllium is desirable in order to facilitate breeding programmes. One approach is to study the distribution of repetitive DNA sequences among species thought on taxonomic grounds, to be closely related. We have used fluorescent in-situ hybridisation (FISH) to examine seven species within sect.Cepa of the genus (A. altaicum, A. cepa, A. fistulosum, A. galanthum, A. pskemense, A. oschaninii andA. vavilovii), one species from sect.Rhizirideum (A. roylei), two species from sect.Allium (A. sativum andA. porrum) and one species from sect.Schoenoprasum (A. schoenoprasum). Each species was probed using a 375 bp repeat sequence isolated fromA. cepa (Barnes & al. 1985), which was generated and labelled by polymerase chain reaction (PCR). No signals were detected in anyAllium species not belonging to sect.Cepa with the exception ofA. roylei, whose designation in sect.Rhizirideum is now questioned. Within sect.Cepa the probe was found to hybridize to the ‘terminal’ regions of the chromosome arms of all the species examined. In addition a number of interstitial bands were detected. Use of FISH reveals a more detailed map of the location of the repeat sequences than has previously been obtained by C-banding and other staining procedures. The distribution of the terminal and interstitial sites when compared, allow us to identify three species groups namely,A. altaicum andA. fistulosum; A. cepa, A. roylei, A. oschaninii andA. vavilovii; andA. galanthum andA. pskemense.

Karyotypic analysis of N-banded chromosomes of diploid alfalfa: Medicago sativa ssp. caerulea and ssp. falcata and their hybrid.

Chromosomes of two diploid (2n = 2x = 16) subspecies of Medicago sativa, ssp. caerulea and ssp. falcata, and their hybrid were studied using an N-banding technique. This study was undertaken to develop an N-banded karyotype of ssp. caerulea and ssp. falcata, and determine if the same technique could be used to identify parental chromosomes in hybrids. The chromosomes of ssp. falcata have only centromeric N bands and thus individual chromosomes could not be identified. However, chromosome-specific bands were observed in ssp. caerulea enabling the identification of each of the eight pairs of chromosomes and the development of an idiogram. All chromosomes have a centromeric band and a telomeric band in the short arm. All of the chromosomes, except chromosomes 7 and 8, have interstitial bands in their long arms and chromosome 5 has two faint interstitial bands in its long arm. The satellited chromosome is easily distinguished due to the secondary constriction and characteristic band at the nucleolar organizer region. The differences in banding patterns between these subspecies makes it possible to distinguish chromosomes from each other in their hybrids. This is the first report of the use of N banding to identify the diploid chromosomes of M. sativa ssp. caerulea and ssp. falcata.

Heterogeneity and meiotic behaviour of B and sex chromosomes, banding patterns and localization of (TTAGGG)n sequences by fluorescence in situ hybridization in the neotropical water rat Nectomys (Rodentia, Cricetidae).

A cytogenetic study using fluorescence in situ hybridization (FISH) of telomere probes, CBG, GTG and RBG banding patterns and synaptonemal complex data was carried out in 41 specimens of Nectomys from three Brazilian states: Pernambuco, Mato Grosso and São Paulo. The specimens presented 2n = 52, 53, 56 and 57, and the differences in chromosome number were due to the presence of three different supernumeraries and also to the occurrence of tandem fusions. The tandem fusions involved chromosome pairs 3 + 11 and 5 + 24 from karyotype with 2n = 56 that originated pairs 1 and 4 in specimens with 2n = 52. Sex chromosome polymorphism was also detected, and the X presented three different morphologies, which could be explained by heterochromatin addition/deletion. FISH results revealed interstitial telomeric bands (ITBs) in a submetacentric B, but no ITB was detected in the chromosomes originated by tandem fusion. The supernumeraries presented a remarkable heterogeneity of size and morphology, constitutive heterochromatin pattern and localization of telomeric sequences. Synaptonemal complex by light and electron microscopy showed the supernumerary as an autopaired univalent. The sex chromosome pairing in meiotic cells involved the heterochromatic short arm of the X chromosome and the short arm of the Y chromosome.

Karyotypic analysis of C-banded chromosomes of diploid alfalfa: Medicago sativa ssp. caerulea and ssp. falcata and their hybrid.

Chromosomes of two diploid (2n = 2x = 16) subspecies of Medicago sativa ssp. caerulea and ssp. falcata and their hybrid were studied by C-banding. This study was undertaken to improve the C-banding technique for alfalfa chromosomes, develop a C-banded karyotype of the ssp. caerulea and ssp. falcata, and determine if the same C-banding technique could be used to identify parental chromosomes in hybrids. The chromosomes of ssp. falcata have only centromeric bands and thus individual chromosomes could not be identified. One accession of ssp. falcata displayed an interstitial band in the middle of the long arm on the satellite chromosome. However, chromosome-specific bands were observed in ssp. caerulea enabling the identification of each of the eight pairs of chromosomes and the development of a idiogram. All chromosomes had centromeric bands and a terminal band in the short arm except the satellite chromosome (chromosome 8). Interstitial bands were also observed in the short arms, with the exception of chromosome 7. Chromosomes 1, 2, 3, and 8 each had one prominent interstitial band in their long arm. The satellited chromosome is easy to identify because of the presence of the secondary constriction, two bands located on either side of the nucleolar organizer region, and a large terminal band on its long arm. The differences in banding patterns between these subspecies allowed the identification of parental chromosomes in hybrid cells.

Procedure for rapid spectroscopic control of the distribution of oxygen and of doping impurities in silicon ingots

Spectral dependences of the coefficients of absorption by free carriers and of multiphoton absorption by a silicon lattice in the region of the interstitial oxygen band at 5.8 μm are established. A procedure for measurement of the distribution of oxygen and alloying impurities in silicon ingots is given. The effectiveness of the spectrometers developed for controlling the segregation of impurities and nonstationary convection of the silicon melt in growing ingots by the Czochralski method is shown.

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.

Chromosomal characterization ofCalomys musculinus(Rodentia, Cricetidae)

SUMMARYThe chromosomes of the South American rodent Calomys musculinus have been analyzed by standard Giemsa C-banding, chromomycin A3, distamycin A and DAPI fluorochrome staining and “in situ” digestion with the restriction endonucleases Alul, HaeIII and HindIII. Constitutive heterochromatin is restricted to the centric regions, and fluoresces after either chromomycin A3 or DAPI treatments, indicating the co-existence of AT and GC-rich sequences in these regions. The restriction enzymes assayed induce diffuse, overlapping patterns of centric and interstitial bands in the chromosomes of this species. Our results agree with other authors' biochemical analyses that indicate the existence of moderately to highly repetitive DNA sequences in C. musculinus that do not appear as a satellite in neutral CsCI DNA gradients, as well as a great abundance of the cleavage sites of these restriction enzymes in the genome of this rodent.

Scanning electron microscopy of heterochromatin in chromosome spreads of male germ cells in Schistocerca gregaria (Acrididae, Orthoptera) after trypsinization.

Chromosome spreads, prepared from testes of the desert locust Schistocerca gregaria, were analyzed using scanning electron microscopy (SEM) after varying periods of preincubation in trypsin. The emphasis of the study was on the appearance of heterochromatin. A trypsin pretreatment of 5 sec resulted in a smooth surface on the chromatin throughout and the heterochromatin was highly electron-emissive. The facultatively heterochromatic X chromosome was clearly visible in interphase spermatogonia and in pachytene and late prophase I spermatocytes. Chromomeres of autosomal bivalents could be recognized in pachytene cells. Centromeric heterochromatin segments were very prominent in autosomes of late prophase I spermatocytes and some chromosomes showed interstitial and telomeric bands. Longer trypsin treatment (10 sec) resulted in a fine globular surface on the chromatin; however, the electron emission of heterochromatic chromosome segments was lower under these conditions. The result of trypsin pretreatment of euchromatin differed only slightly from that of the heterochromatin. Extensive trypsin treatment (20 sec) did not alter further the relative electron emission of heterochromatin and euchromatin, but the regular globular appearance was lost, apparently owing to damage on the chromatin surface. The loss of electron emission from the centromeric heterochromatin of the autosomes and the facultatively heterochromatic X chromosome after extended trypsin treatment suggests a central role of proteins in mediating the heterochromatic status in meiotic chromosomes of the locust. Information obtained using scanning electron microscopy of chromosome spreads is complementary to that obtained by C-banding in that facultative heterochromatin is visualized with particular clarity.

Satellite DNAs, Heterochromatin and sex chromosomes in Chionodraco hamatus (Channichthyidae, Perciformes)

We studied the genome of an antarctic ice fish, Chionodraco hamatus, in order to detect highly repetitive DNAs that may play a role in heterochromatinization processes and sex chromosome differentiation. We used two different experimental approaches. Hybridization of a Bkm probe to genomic DNA showed slight differences between the two sexes. Using restriction enzymes, a Bgl II satellite (pIF) was isolated. In situ hybridization revealed a preferential localization of pIF on the centromeres and the telomeres of most chromosomes, as well as an interstitial band on the long arms of the neo-Y sex chromosome, where probably the hypothetical fusion took place. Dot-blot experiments showed that pIF is still present in species belonging to different families of the same suborder. Though preliminary, our results suggest a conservative nature of this DNA which might have played a definite functional role in the genome of these polar fishes.

Karyotypes and C-banding patterns in species of Cyphomandra Mart. ex Sendtner (Solanaceae)

The orcein and C-banded karyotypes of 11 species of Cyphomandra (Solanaceae) were described. All species were diploid with 2 n = 2 x = 24. The chromosomes were large, ranging from 4 to 10 μm in length, and in each complement were largely metacentric or submetacentric with few subtelocentrics. There was a significant negative correlation between chromosome length and arm ratio within a complement as well as between taxa. In general, chromosomes of the larger complements were more symmetrical in terms of both relative chromosome length and arm ratio, implying that similar amounts of DNA had been added to or taken away from every chromosome are of each complement during evolutionary divergence. Two pairs of non-homologous chromosomes were seen to contain subterminal secondary constrictions in most species. The two Brazilian species studied differed from those of Andean origin in the location of one of these secondary constrictions, suggesting a major evolutionary divergence between these two groups of species. Non-homologous chromosomes were difficult to distinguish from one another without the aid of C-banding, due to a continuum in the distribution of chromosome lengths and arm ratios. Telomeric and interstitial bands were shown in all species but not all chromosomes in each complement were banded. There were no centromeric bands. Nuclear DNA amount and the length, but not proportional length, of C-bands were correlated in each species. One species ( C. luteoalba (Pcrs.) Child, section Cyphomandropsis ) was unique in its banding pattern, providing further evidence for the delimitatation of this species and perhaps section from other Cyphomandra taxa.

Karyotypes and C-banding patterns in species of Cyphomandra Mart. ex Sendtner (Solanaceae)

The orcein and C-banded karyotypes of 11 species of Cyphomandra (Solanaceae) were described. All species were diploid with 2n = 2x = 24. The chromosomes were large, ranging from 4 to 10 μm in length, and in each complement were largely metacentric or submetacentric with few subtelocentrics. There was a significant negative correlation between chromosome length and arm ratio within a complement as well as between taxa. In general, chromosomes of the larger complements were more symmetrical in terms of both relative chromosome length and arm ratio, implying that similar amounts of DNA had been added to or taken away from every chromosome are of each complement during evolutionary divergence. Two pairs of non-homologous chromosomes were seen to contain subterminal secondary constrictions in most species. The two Brazilian species studied differed from those of Andean origin in the location of one of these secondary constrictions, suggesting a major evolutionary divergence between these two groups of species. Non-homologous chromosomes were difficult to distinguish from one another without the aid of C-banding, due to a continuum in the distribution of chromosome lengths and arm ratios. Telomeric and interstitial bands were shown in all species but not all chromosomes in each complement were banded. There were no centromeric bands. Nuclear DNA amount and the length, but not proportional length, of C-bands were correlated in each species. One species (C. luteoalba (Pcrs.) Child, section Cyphomandropsis) was unique in its banding pattern, providing further evidence for the delimitatation of this species and perhaps section from other Cyphomandra taxa.

Cytogenetic studies on Bacillus grandii grandii and B. grandii benazzii (Insecta, Phasmatodea): karyotype description, constitutive heterochromatin and nucleolus organizer regions

The karyotype of the new Sicilian subspecies Bacillus grandii benazzii is described and compared to that of B. g. grandii. Both taxa share constant, very similar chromosome sets with 2n=34, XX, female and 2n=33, XO, male, the sex chromosomes being the third element of the complement. C-banding reveals that a centromeric heterochromatin mass is present on all chromosomes, but no interstitial bands are observed. Differences between karyotypes reside in the satellites which are located on pairs 13 and 16 in B. g. benazzii and only on pair 16 in B. g. grandii, in contracted metaphases larger satellites are positively C-banded. Furthermore, Ag-detected NORs are seen on pair 13 in B. g. benazzii and on pair 16 in B. g. grandii. Relationships between constitutive heterochromatin and NORs, NOR heteromorphism and the position of the 34-chromosome taxa within the genus are discussed.

The Giemsa C‐Banded Karyotype of Canada Wildrye (Elymus canadensis)

AbstractKaryotype of Canada wildrye (Elymus canadenisis L.) was described using giemsa C‐banding techniques. Most of the chromosomes showed dome banding pattern polymorphism. Small to large terminal and centormere bands were observed in most of the chromosomes. A faint satellite was observed in one chromosome. Tow chromosomes had a large interstitial band near the centromeres in the long arms. The Giemsa C‐banding pattern of E. Canadensis is compared to that of Pseudoroegneria spicata and Critesion boddanii to illustrate species relationship.

Banding patterns of the holocentric chromosomes in some species of Heteroptera.

Spermatogonial metaphase chromosomes of Petillia patullicollis, Leptocorisa acuta and Ochrochira granulipes reveal C-bands, while G-bands are encountered in some chromosomes of Iphita limbata, Anoplocnemis phasiana and Leptocorisa acuta. The most frequent location of C-heterochromatin occurs in telomeric regions. Interstitial bands are very scarce. Difference in the size of subtelomeric C-heterochromatin block has been observed in the largest chromosome of L. acuta. Satellite-like structures are encountered in chromosomes 1 and 3 of N. icterica and A. phasiana respectively. The banding results are compared with the few reports available on banding of heteropteran chromosomes. It is suggested from our analysis that if C-bands are present, they are preferentially located at telomeric regions of chromosomes. G-band distributions are, however, not discrete enough to identify all the chromosomes of the complement.

Novel C-Banding Patterns in Paragonimus ohirai (Trematoda: Platyhelminthes)

The C-banding pattern for the karyotype of Paragonimus ohirai representing individuals in a new population is reported. The short arm of chromosome 4 consisted of a large pericentromeric proximal C-band block and euchromatic tip. This pattern has not been observed previously and is designated as type E. Other new observations were: chromosome 5 was composed of pericentromeric heterochromatin, a lightly stained intercalary band at the middle portion of the short arm, and a lightly stained interstitial band at the terminal region of the long arm. Chromosome 7 consisted of pericentromeric heterochromatin and a lightly stained telomeric band at the short arm.

A Study of Chromosomes and Their C-Band Patterns in Seven Species of Acrididae (Orthoptera)

SUMMARYChromosomes and their C-band patterns in seven orthopteran species belonging to family Acrididae were studied. Though all these species are characterised by an apparently uniform karyotype of 2n O = 23 X0, they exhibit considerable variation in the relative length and C-band patterns of their chromosomes. While paracentromeric C-bands are uniformly located in all karyotypes, the distribution of interstitial and telomeric bands is found to be variable in these species in general and in two species of Oxya in particular. Importance of C-band as a tool for separating karyologically indistinguishable species has been emphasized.

Heterochromatin differentiation and phylogenetic relationship of the A genomes in diploid and polyploid wheats

Heterochromatin differentiation, including band size, sites, and Giemsa staining intensity, was analyzed by the HKG (HCl-KOH-Giemsa) banding technique in the A genomes of 21 diploid (Triticum urartu, T. boeoticum and T. monococcum), 13 tetraploid (T. araraticum, T. timopheevi, T. dicoccoides and T. turgidum var. Dicoccon, Polonicum), and 7 cultivars of hexaploid (T. aestivum) wheats from different germplasm collections. Among wild and cultivated diploid taxa, heterochromatin was located mainly at centromeric regions, but the size and staining intensity were distinct and some accessions' genomes had interstitial and telomeric bands. Among wild and cultivated polyploid wheats, heterochromatin exhibited bifurcated differentiation. Heterochromatinization occurred in chromosomes 4A(t) and 7A(t) and in smaller amounts in 2A(t), 3A(t), 5A(t), and 6A(t) within the genomes of the tetraploid Timopheevi group (T. araraticum, and T. timopheevi) and vice versa within those of the Emmer group (T. dicoccoides and T. turgidum). Similar divergence patterns occurred among chromosome 4A(a) and 7A(a) of cultivars of hexaploid wheat (T. aestivum). These dynamic processes could be related to geographic distribution and to natural and artifical selection. Comparison of the A genomes of diploid wheats with those of polyploid wheats shows that the A genomes in existing diploid wheats could not be the direct donors of those in polyploid wheats, but that the extant taxa of diploids and polyploids probably have a common origin and share a common A-genomelike ancestor.

Supernumerary chromosome system, C-banding pattern characterization and multiple nucleolus organizer regions in Moenkhausia sanctaefilomenae (Pisces, Characidae)

Chromosomes of Moenkhausia sanctaefilomenae (10 males and 20 females) collected from a tributary of the Tiete River (Botucatu, S.P. Brazil) were examined using kidney and testicular cells. Both males and females presented 2n=50 chromosomes and 1 to 8 small supernumerary microchromosomes. C-banding demonstrated positively stained heterochromatic blocks in almost every chromosome and a pattern of interstitial bands located in the same position in relation to the centromere on the long arm of a large number of chromosomes. Two large NORs were detected in pair 19 of all the silver-stained metaphases; zero to 6 additional small NORs were detected in other chromosomes. A general survey of the occurrence of supernumerary chromosomes in fishes is presented.

C-banding and DNA content in three species of Belostoma (Heteroptera) with large differences in chromosome size and number

C-banding was carried out on Belostoma elegans (2n=26+X1X2Y) (♂), B. micantulum (2n=14+XY) (♂) and B. oxyurum (2n=6+XY) (♂) (Belostomatidae, Heteroptera). The C-bands always have a telomeric localization and no interstitial bands were detected. An inverse relationship between chromosome size and chromosome number exists, and besides, an inverse relationship between chromosome size and the size of the C-bands was observed. The DNA content was determined in all three species. B. elegans has a C content of 1.55±0.06 pg, B. micantulum has 0.88±0.04 pg and B. oxyurum had 0.53±0.04 pg.

A Technique for C-Banding Plant Chromosomes with Wright Stain

A technique is presented for C-banding plant chromosomes with a modified Wright stain. This procedure consistently produces brightly stained, well defined telomeric and interstitial heterochromatic bands, identifiable centromeric constrictions, and lightly stained euchromatic areas on chromosomes of rye.