Silver staining of the centromeric area of acrocentric and Robertsonian metacentric mouse chromosomes

A silver stain (Kt) technique was used to analyze the centromeric area in metacentric chromosomes originating from Robertsonian rearrangements in the mouse. The 2n=40 all-acrocentric mouse karyotype and two Robertsonian-rearranged karyotypes (2n=24 and 2n=26 from Upper Valtellina) were used. The existence was demonstrated of a single centromeric pattern common to metacentric and to acrocentric chromosomes except for the Y, and consisting of two deeply stained dots, one per chromatid. In many cells this technique stains the nucleolar organizers and resolves the paracentromeric constitutive heterochromatin in chromomeres.     

Characterisation of pericentrometric and sticky intercalary heterochromatin in Ornithogalum longibracteatum (Hyacinthaceae)

The hexaploid liliaceous plant Ornithogalum longibracteatum (2n=6x=54) has a heterochromatin-rich bimodal karyotype with large (L) and small (S) chromosomes. The composition and subgenomic distribution of heterochromatin was studied using molecular and cytological methods. The major component of centromeric heterochromatin in all chromosomes is Satl, an abundant satellite DNA with a basic repeat unit of 155 bp and an average A+T content (54%). The major component of the large blocks of intercalary heterochromatin in L chromosomes is Sat2, an abundant satellite DNA with a basic repeat unit of 115 bp and a high A+T content (76%). Additionally, traces of Sat2 can be detected at the centromeric regions of S chromosomes, while minor amounts of Satl are discernible in intercalary heterochromatin of L chromosomes. The chromosomal localisation pattern of Sat2 is consistent with the fluorescent staining pattern obtained with the A+T-specific DNA ligand 4'-6-diamidino-2-phenylindole (DAPI). A+T-rich intercalary heterochromatin is sticky and tends to associate ectopically during mitosis. Sister chromatid exchange clustering was found at the junctions between euchromatin and heterochromatin and at the centromeres. The pattern of mitosis-specific phosphorylation of histone H3 was not uniform along the length of the chromosomes. In all L and S chromosomes, from early prophase to ana-/telophase, there is hyperphosphorylation of histone H3 in the pericentromeric chromatin and a slightly elevated phosphorylated histone H3 level at the intercalary heterochromatin of L chromosomes. Consequently, the overall phosphorylated histone H3 metaphase labelling resembles the distribution of Satl in the karyotype of O. longibracteatum.     

Mapping the distribution of the telomeric sequence (T(2)AG(3))(n) in rock wallabies,Petrogale (Marsupialia: Macropodidae), by fluorescence in situ hybridization. ii. the lateralis complex

The distribution of the conserved vertebrate telomeric sequence (T(2)AG(3))(n) was examined by fluorescence in situ hybridization in the six Petrogale (rock wallabies) taxa of the lateralis complex. As expected, the (T(2)AG(3))(n) sequence was located at the termini of all chromosomes in all taxa. However, the sequence was also present at several nontelomeric (viz., interstitial and centromeric) sites. The signals identified were associated with either ancient rearrangements involved with the formation of the 2n = 22 plesiomorphic macropodine karyotype or more recent rearrangements associated with karyotypes derived from the 2n = 22 karyotype. Interstitial (T(2)AG(3))(n) signals identified on chromosomes 3 and 4 in all six species of the lateralis complex and a large centromeric signal identified on chromosome 7 in the five subspecies/races of P. lateralis appear to be related to the more ancient rearrangements. Subsequent chromosome evolution has seen these signals retained, lost, or amplified in different Petrogale lineages. Within the lateralis complex, in two submetacentric chromosome derived by recent centric fusions, the telomeric sequence was identified at or near the centromere, indicating its retention during the fusion process. In the two taxa where chromosome 3 was rearranged via a recent centromeric transposition to become an acrocentric chromosome, the telomeric signal was located interstitially.     

Karyotype description of two species of Hypostomus (Siluriformes, Loricariidae) of the Planalto da Bodoquena, Brazil

Hypostomus sp 3-Córrego Salobrinha NUP 4247 and Hypostomus sp 2-Rio Perdido NUP 4249, collected in the Planalto da Bodoquena, Paraguay River basin, Brazil, were characterized cytogenetically. Hypostomus sp 3-Córrego Salobrinha showed two modal numbers. This polymorphism consists of the presence of two extrachromosomes. It was not possible to define the diploid number in four specimens, where cell lineages had 2n = 83 and 2n = 84 chromosomes in one individual, and 2n = 82, 2n = 83 and 2n = 84 chromosomes in the others. These results reveal the existence of a genetic mosaic due to the occurrence of one or two extrachromosomes in this species. Hypostomus sp 2-Rio Perdido NUP 4249 showed a 2n = 84, FN = 106 with size heteromorphism in one pair of chromosomes stained with AgNO3. In both species, C banding showed a pattern of heterochromatin distribution with a few small bands in the centromeric and pericentromeric regions coinciding with chromomycin A3 staining. Until now, the major diploid number for the genus Hypostomus was 2n = 80, but the species studied here had chromosomes that in creased this number and the variation for this genus. Our results are also the first cytogenetic data on Hypostomus from the Paraguay River basin.     

Cytogenetic analysis of some Brazilian marsupials (Didelphidae: Marsupialia)

Three species of marsupials from the Amazon region (Marmosa cinerea, Caluromys lanatus, and Didelphis marsupialis) and two from the region of S?o Paulo (Didelphis marsupialis and Didelphis albiventris) were studied. The G-banding pattern of the species with 2n = 14 (M. cinerea and C. lanatus) was very similar, as well as the pattern of G-bands in the species with 22 chromosomes (Didelphis). All of the autosomes of M. cinerea and D. albiventris have centromeric C-bands and the Y chromosome is totally C-band positive. The long arm of the M. cinerea X chromosome is completely C-band positive except for a negative band close to the centromeric region. In D. albiventris the long arm of the X chromosome is C-band positive except for a negative band close to the telomeric region. In M. cinerea the silver-stained nucleolar organizer regions (Ag-NORs) are found in the acrocentric chromosomes, being located in the telomeric region of one pair and in the centromeric region of the other pair. Caluromys lanatus has centromeric Ag-NORs in one acrocentric and in one submetacentric chromosome pairs. Didelphis marsupialis has three chromosome pairs with telomeric Ag-NORs. In D. albiventris the Ag-NORs are terminal and located in both arms of one pair and in the long arm of two pairs of chromosomes.     

Karyotype analysis and physical mapping of 45S rDNA in eight species of Sophora,Robinia, and Amorpha

The karyotype analysis and physical locations of 45S rDNA were carried out by means of fluorescence in situ hybridization in three species,and two forms of Sophora,two species of Robina,and one species of Amorpha.S.japonica L.,S.japonica L.f.oligophylla Franch.,S.japonica L.f.pendula Loud.,and S.xanthantha C.Y.Ma.are all tetraploids with 2n=28.There were four 45S rDNA sites in pericentromeric regions of two Pairs of chromosomes in each of them.S.rubriflora Tsoong.is a triploid with 2n=21,and three sites were located in each satellite of group 5 chromosomes.In R.pseudoacacia L.(2n=2x=22),we examined four intensive signals in telomeric regions of two pairs of satellite chromosomes.In R.hispida L.(2n=2x=30),there were four other signals in centromeric regions besides those like in R.pseudoacacia.Amorpha fruticosa L.has most chromosomes(2n=40)among the eight materials,however,there were only six 45S rDNA loci and they laid in centromeric regions,and satellites of three pairs of chromosomes.45S rDNA is a valuable chromosomal landmark in karyotype analysis.The distribution and genomic organization Of rDNA in the three genera were also discussed.     

豆科三属八种植物的核型及rDNA定位研究

对豆科槐属的国槐(SophorajaponicaL.)、五叶槐(S.japonicaL.f.oligophyllaFranch.)、龙爪槐(S.japonicaL.f·pendulaLoud.)、黄金槐(S.xanthanthaC.Y.Ma.)(以上均为四倍体,2n=4x=28)、红花槐(S.rubrifloraTsoong.,2n=3x=21),刺槐属的刺槐(Robiniapseudoa-caciaL.,2n=2x=22)、毛洋槐(R.hispidaL.,2n=2x=30)和紫穗槐属的紫穗槐(AmorphafruticosaL.,2n=2x=40)核型进行了分析,并应用荧光原位杂交技术进行了45SrDNA的染色体定位。槐属4个四倍体种各具4个45SrDNA位点,位于两对染色体的着丝粒周围;红花槐,3个45SrDNA位点位于第5组染色体随体区域。刺槐,4个rDNA位点位于两对随体染色体端部;毛洋槐,8个rDNA位点,4个位于两对染色体的随体及次缢痕,另4个位于两对染色体着丝粒周围。紫穗槐,6个45SrDNA位点,分别位于3对染色体的着丝粒和随体。本文对rDNA作为染色体标记在核型分析中的应用及在基因组中的分布特点进行了讨论。     

Fluram induces species-dependent C and G bands in mammalian chromosomes, revealing heterogeneous distribution of chromosomal proteins

Fluram (Fluorescamine; 4-phenylspiro(furan-2(3H),1'-phthalan)-3,3'-dione) is a fluorogenic reagent, which permits the detection of primary amines by forming highly fluorescent pyrrolinone derivatives. This reagent has been used on methanol-acetic acid fixed metaphase chromosomes of mouse and man and proved to be very effective in differentiating chromosome regions in both genomes. Mouse centromeric heterochromatin is highly reactive, showing intense fluorescence in all centromeric regions, whereas human chromosomes show no fluorescence in such regions. In addition, a G-like banding pattern is also obtained in both types of chromosomes. The differential reactivity of each chromosome region showed by this method demonstrates a heterogeneous distribution of chromosome proteins, resulting in a chromosome banding pattern, which is in this case species dependent.     

Cytogenetic analysis of Astylus antis (Perty, 1830) (Coleoptera, Melyridae): Karyotype, heterochromatin and location of ribosomal genes

Cytogenetic analysis of Astylus antis using mitotic and meiotic cells was performed to characterize the haploid and diploid numbers, sex determination system, chromosome morphology, constitutive heterochromatin distribution pattern and chromosomes carrying nucleolus organizer regions (NORs). Analysis of spermatogonial metaphase cells revealed the diploid number 2n = 18, with mostly metacentric chromosomes. Metaphase I cells exhibited 2n = 8II+Xyp and a parachute configuration of the sex chromosomes. Spermatogonial metaphase cells submitted to C-banding showed the presence of small dots of constitutive heterochromatin in the centromeric regions of nearly all the autosomes and on the short arm of the X chromosome (Xp), as well as an additional band on one of the arms of pair 1. Mitotic cells submitted to double staining with base-specific fluorochromes (DAPI-CMA(3) ) revealed no regions rich in A+T or G+C sequences. Analysis of spermatogonial mitotic cells after sequential Giemsa/AgNO (3) staining did not reveal any specific mark on the chromosomes. Meiotic metaphase I cells stained with silver nitrate revealed a strong impregnation associated to the sex chromosomes, and in situ hybridization with an 18S rDNA probe showed ribosomal cistrons in an autosomal bivalent.     

中国两种掌突蟾(锄足蟾科Pelobatidae,无尾目Anura)的细胞遗传学研究

本文对分布于云南境内的两种Leptolalax——L.ventripunctatus和L.alpinus的常规Giemsa核型、C-带和Ag-NORs作了研究,结果表明L.ventripunctatus的2n=22,20M 2T,NF=42,1对Ag-NORs位于5(?),并呈现异形现象,该区域亦显C-带正染;L.alpinus 2n=24,14M 4SM 6T,NF=42,1对Ag-NORs位于No.8短臂端部,并有随体联合现象。两种的着丝点区域均呈现C-带正染。     

High-resolution HKG-banding in maize mitotic chromosomes

Root-tip maize chromosomes (2n=20) were prepared by high-resolution procedures after ethidium bromide/colchicine synchronization. Using HKG-banding (HCl−KOH-Giemsa), that shows both centromeric and intercalary heterochromatin, the banding pattern of the elongated-chromosomes showed one to nine well-resolved dark bands. Differences of HKG-banding pattern of elongated and compacted chromosomes were performed by image analysis.     

Cytotypes of Kirk's dik-dik (Madoqua kirkii,Bovidae) show multiple tandem fusions

Madoqua kirkii, a miniature African antelope, is noted for extensive chromosomal variation that has been categorized in four distinct cytotypes (A-D). In this investigation, we analyzed the A cytotype (2n = 46, FN = 48) using a suite of molecular cytogenetic approaches that entailed (i) whole chromosome and subchromosomal painting by fluorescence in situ hybridization (FISH), (ii) the study of Madoqua centromeric-specific DNA derived from pooled DNA obtained from the centromeric regions of the acrocentric chromosomes, and (iii) DNA from the telomere:centromere junctions of tandemly fused chromosomes. DNA from these sources was used to probe for the persistence of interstitial satellite DNA and residual centromeric sequences in the tandem and centric fusion junctions by PCR and FISH. The analyses show centromeric sequences at two of the six tandem fusion junctions. These data, and those of hybrid specimens (A × B cytotypes) in conjunction with published information permitted an interpretation of the probable sequence of chromosomal rearrangements among the M. kirkii cytotypes. We discuss the findings in the context of chromosomal evolution in these antelopes, and the implications that these hold for ex-situ breeding programs of the species.     

Chromosome Studies of 10 Chinese Species of Adenophora Fisch.

This paper is a cytological part of biosystematic studies on Adenophora Fisch. in Heilongjiang, China. Chromosomal numbers and karyotypes of 10 spp. and 1 var. are reported. The results are summarized in Table 1. The chromosomal numbers and karyotypes of 6 spp. and 1 var. are first reported, including tetraploid species (2n=68) (A. pereskiifolia var. alternifolia, A. amurica and A. gmelinii). The basic number of chromosomes in the genus is mainly 17 (x=17), but that of A. trachelioides and A. remotiflora (2n=36) is 18 (x=18), an unique one in the genus. The karyotypes of all the species examined are relatively uniform, which means that they are derived from a common ancestral type. The chromosomes are smaller, varying between 2-4 μm. The majority of chromosomes are m and sm ones. And a pair of sat-chromosomes and a pair of st chromosomes are always present. The centromeric terminalization value of chromosomes is 57.5-61.9%, showing higher symmetry of karyotypes in the genus. The karyotype of A. tetraphylla (2n=34) is the most symmetrical among these species. Based on its morphological characters and distribution, the species may be considered as a relatively primitive member of the genus. The results show two revolutionary trends in karyotypes of the genus: number variation (including polyploidy and aneuploidy) and structural variation. The polyploidy is one of the principal patterns of speciation in the genus. Combined with the other characters, these species are taxonomically discussed, and two new taxa (A. amurica Fu et Liu and A. pereskiifolia ssp. alternifolia (Fuh ex Y. Z. Zhao) Fu et Liu) are confirmed. A. trachelioides and A. remotiflora (both 2n=36) with obvious petioles seems more advanced than the other species (2n 34).     

A comparative banding analysis of chromosomes in three species of lemurs (Primates,Lemuridae)

Banded karyotypes were compared in 3 species of lemurs,Lemur catta (2n=56),L. f. fulvus (2n=60) andL. mongoz (2n=60). The karyotypes of the latter 2 species were indistinguishable from each other in both Q-band and G-band patterns, except thatL. mongoz had an unusually large Y chromosome. The karyotypic differences betweenL. catta and the other 2 species were mainly explained by centric fusions (or fissions) and pericentric inversions. Contrary to the general similarity in Q-band and G-band patterns, the C-band patterns were highly variable among the 3 species. All chromosomes ofL. fulvus had a distinctive C-band in the centromeric region, whileL. mongoz had only a few chromosomes with an apparent C-band.L. catta was remarkable by showing interstitial and terminal C-bands in some elements, in addition to the centromeric band which was observed in about 20 pairs.     

Karyotypic conservatism in samples of Characidium cf. zebra (Teleostei, Characiformes, Crenuchidae): Physical mapping of ribosomal genes and natural triploidy

Basic and molecular cytogenetic analyses were performed in specimens of Characidium cf. zebra from five collection sites located throughout the Tietê, Paranapanema and Paraguay river basins. The diploid number in specimens from all samples was 2n = 50 with a karyotype composed of 32 metacentric and 18 submetacentric chromosomes in both males and females. Constitutive heterochromatin was present at the centromeric regions of all chromosomes and pair 23, had additional interstitial heterochromatic blocks on its long arms. The nucleolar organizer regions (NORs) were located on the long arms of pair 23, while the 5S rDNA sites were detected in different chromosomes among the studied samples. One specimen from the Alambari river was a natural triploid and had two extra chromosomes, resulting in 2n = 77. The remarkable karyotypic similarity among the specimens of C. cf. zebra suggests a close evolutionary relationship. On the other hand, the distinct patterns of 5S rDNA distribution may be the result of gene flow constraints during their evolutionary history.     

Identification and designation of telocentric chromosomes in barley by means of Giemsa N-banding technique

Summary Seven complete chromosomes and nine telocentric chromosomes in telotrisomics of barley (Hordeum vulgare L.) were identified and designated by an improved Giemsa N-banding technique. Karyotype analysis and Giemsa N-banding patterns of complete and telocentric chromosomes at somatic late prophase, prometaphase and metaphase have shown the following results: Chromosome 1 is a median chromosome with a long arm (Telo 1L) carrying a centromeric band, while short arm (Telo 1S) has a centromeric band and two intercalary bands. Chromosome 2 is the longest in the barley chromosome complement. Both arms show a centromeric band, an intercalary band and two faint dots on each chromatid at middle to distal regions. The banding pattern of Telo 2L (a centromeric and an intercalary band) and Telo 2S (a centromeric, two intercalary and a terminal band) corresponded to the banding pattern of the long and short arm of chromosome 2. Chromosome 3 is a submedian chromosome and its long arm is the second longest in the barley chromosome complement. Telo 3L has a centromeric (fainter than Telo 3S) and an intercalary band. It also shows a faint dot on each chromatid at distal region. Telo 3S shows a dark centromeric band only. Chromosome 4 is the most heavily banded one in barley chromosome complement. Both arms showed a dark centromeric band. Three dark intercalary bands and faint telomeric dot were observed in the long arm (4L), while two dark intercalary bands in the short arm (4S) were arranged very close to each other and appeared as a single large band in metaphase chromosomes. A faint dot was observed in each chromatid at the distal region in the 4S. Chromosome 5 is the smallest chromosome, which carries a centromeric band and an intercalary band on the long arm. Telo 5L, with a faint centromeric band and an intercalary band, is similar to the long arm. Chromosomes 6 and 7 are satellited chromosomes showing mainly centromeric bands. Telo 6S is identical to the short arm of chromosome 6 with a centromeric band. Telo 3L and Telo 4L were previously designated as Telo 3S and Telo 4S based on the genetic/linkage analysis. However, from the Giemsa banding pattern it is evident that these telocentric chromosomes are not correctly identified and the linkage map for chromosome 3 and 4 should be reversed. One out of ten triple 2S plants studied showed about 50% deficiency in the distal portion of the short arm. Telo 4L also showed a deletion of the distal euchromatic region of the long arm. This deletion (32%) may complicate genetic analysis, as genes located on the deficient segment would show a disomic ratio. It has been clearly demonstrated that the telocentric chromosomes of barley carry half of the centromere. Banding pattern polymorphism was attributed, at least partly, to the mitotic stages and differences in techniques.Contribution from the Department of Agronomy and published with the approval of the Director of the Colorado State University Experiment Station as Scientific Series Paper No. 2730. This research was supported in part by the USDA/SEA Competitive Research Grant 5901-0410-9-0334-0, USDA/ SEA-CSU Cooperative Research Grant 12-14-5001-265 and Colorado State University Hatch Project. This paper was presented partly at the Fourth International Barley Genetics Symposium, Edinburgh, Scotland, July 22–29, 1981     

Computer assisted karyotype analysis of Pyrrhopappus carolinianus

With the help of Computer Aided Karyotyping procedures, Ag-NOR staining and C-banding techniques, the karyotype of Pyrrhopappus carolinianus (Asteraceae, Lactuceae) has been studied. The species has 2n=12 chromosomes. Silver staining reveals that the two shortest pairs of chromosomes possess NOR's. On the basis of chromosome length and centromere position, only the longest chromosome pair and the satellite chromosomes can be identified. Two types of C-banding can be obtained, dependent on the temperature of the hydrochloric acid hydrolysis of the root tips. Hydrolysis at 60°C results exclusively in centromeric bands, whereas a treatment at room temperature reveals a pattern of intercalary bands. A computer assisted analysis of the intercalary banding pattern resulted in the construction of schematic representation of the average C-banding pattern. This banding pattern allows an easy identification of each of the chromosome pairs.     

Karyological studies on Picea ajanensis (Lindl. et Gord.) Fisch. ex Carr. from different regions

Results of karyological study of Picea ajanensis (Lindl. et Gord.) Fisch. ex Carr examined from 13 provenances are presented. In addition to the cytotypes with typical chromosome number (2n = 24), P. ajanensis displays cytotypes with one or two B-chromosomes (2n = 24 + 1 - 2B). Among A-chromosomes, there are 8 pairs of long metacentrics and 4 pairs of shorter meta- or submetacentrics. Among B-chromosomes there are two types of chromosomes: metacentric (B1) and submetacentric (B2) ones. There are many nucleolar chromosomes. Several chromosomes have secondary constrictions. Patterns of B-chromosome distribution within P. ajanensis are have been discussed.