Physical mapping of the 5S ribosomal RNA genes in Arabidopsis thaliana by multi-color fluorescence in situ hybridization with cosmid clones

The 5S ribosomal RNA genes were mapped to mitotic chromosomes of Arabidopsis thaliana by fluorescence in situ hybridization (FISH). In the ecotype Landsberg erecta, hybridization signals appeared on three pairs of chromosomes, two of which were metacentric and the other acrocentric. Hybridization signals on one pair of metacentric chromosomes were much stronger than those on the acrocentric and the other pair of metacentric chromosomes, probably reflecting the number of copies of the genes on the chromosomes. Other ecotypes, Columbia and Wassilewskija, had similar chromosomal distribution of the genes, but the hybridization signals on one pair of metacentric chromosomes were very weak, and detectable only in chromosomes prepared from young flower buds. The chromosomes and arms carrying the 5S rDNA were identified by multi-color FISH with cosmid clones and a centromeric 180 bp repeat as co-probes. The metacentric chromosome 5 and its L arm carries the largest cluster of the genes, and the short arm of acrocentric chromosome 4 carries a small cluster in all three ecotypes. Chromosome 3 had another small cluster of 5S rRNA genes on its L arm. Chromosomes 1 and 2 had no 5S rDNA cluster, but they are morphologically distinguishable; chromosome 1 is metacentric and 2 acrocentric. Using the 5S rDNA as a probe, therefore, all chromosomes of A. thaliana could be identified by FISH. Chromosome 1 is large and metacentric; chromosome 2 is acrocentric carrying 18S-5.8S-25S rDNA clusters on its short arm; chromosome 3 is metacentric carrying a small cluster of 5S rDNA genes on its L arm; chromosome 4 is acrocentric carrying both 18S-5.8S-25S and 5S rDNAs on its short (L) arm; and chromosome 5 is metacentric carrying a large cluster of 5S rDNA on its L arm.     

The characterization of somatic chromosomes of Gymnothorax unicolor (Delaroche, 1809) by C-banding and NOR staining (Osteichthyes,Anguilliformes)

The diploid chromosome number of Gymnothorax unicolor (Delaroche, 1809) is 2n=42, the karyotype comprising six pairs of meta-submetacentric and fifteen pairs of acrocentric chromosomes. C-positive chromatin is present in the centromeres of all chromosomes as well as in the paracentromeric regions of some chromosomes. A nucleolar organizer region was identified on the long arm of chromosome 9, near the centromere. This region is also positive to C-banding.Cytotaxonomical relationships are evidenced between the described karyotype and that of the related species Muraena helena.     

The Karyotype of the flathead sculpin Megalocottus platycephalus taeniopterus (Kner, 1868) (Pisces: Cottidae) from Vostok Bay,Sea of Japan

For the first time, we studied the karyotype of the flathead sculpin Megalocottus platycephalus taeniopterus (Kner, 1868) from Vostok Bay of the Sea of Japan. The karyotype is stable: 2n = 42 (2 metacentric, 2 submeta-subtelocentric, 30 subtelocentric, and 8 acrocentric chromosomes), NF = 44 + 2. The nucleolar organizers (NOs) were identified using Ag banding in two pairs of chromosomes: in the telomeric parts of the short arm of the medium-size subtelocentric chromosome and the long arm of the large acrocentric chromosome. Variations in the number of nucleolar organizer chromosomes and in the number of NO staining blocks were found. Comparison of the karyotypes of M. p. taeniopterus and previously studied M. p. platycephalus (Pallas, 1814) from the northern Sea of Okhotsk revealed their similarity in the number and morphology of chromosomes and the number of chromosome arms and difference between the subspecies in the number and location of NO, which allows their discrimination.     

Karyotype and divergence of stream Dolly Varden from the Southern Sakhalin

The karyotype of stream Dolly Varden inhabiting a tributary of the Belaya River (the basin of Naiba River, southern Sakhalin) was determined (2n = 82 and NF = 98 + 2). According to the main characteristics (chromosome number and arm number, the presence of a pair of marker submeta-subtelocentric chromosomes with nucleolus organizer regions (NORs), one pair of large acrocentric chromosomes, and one pair of subtelocentric chromosomes), this karyotype is identical to the karyotype of anadromous southern Dolly Varden from Salvelinus malma krasheninnikovi of Primorye and Japan. However, in most stream Dolly Varden individuals, additional active nucleolus organizer regions (NORs) located in telomeric and paracentric regions of two to three pairs of acrocentric chromosomes were revealed. It is suggested that the stream and anadromous southern forms of Dolly Varden are evolutionarily related NORs that are silent in the anadromous souther form are active in the stream form. Possible causes of these differences in NOR activity are discussed.     

Constitutive heterochromatin variation in two species of rattus with apparently similar karyotypes

Rattus blanfordi and R. cutchicus medius both have a chromosome complement of 2n=36 and all chromosomes except the submetacentric Y of R. blanfordi are acrocentric. The apparently similar karyotypes of the two species, however, show variations in the nature and quantity of C-band-positive constitutive heterochromatin (C-heterochromatin) as revealed by C- and G-banding and Hoechst 33258 fluorescence. R. blanfordi with large-sized X and Y chromosomes and conspicuously larger centromeric heterochromatin in all the autosomes as compared to that of R. cutchicus medius has much more C-heterochromatin in its genome than the latter. The variation in the quantity of C-heterochromatin has been accomplished without altering the morphology of the acrocentric chromosomes unlike other mammals in which variations have been reported to result generally in the addition or deletion of a totally heterochromatic second arm.     

Occurrence of two cytotypes in <Emphasis Type="Italic">Bryconamericus</Emphasis> aff. <Emphasis Type="Italic">iheringii</Emphasis> (Characidae): karyotype analysis by C- and G-banding and replication bands

Cytogenetic analyses of Bryconamericus aff. iheringii specimens from the upper Paraná River basin (State of Paraná, Brazil) are provided. They had 2n = 52 chromosomes and two cytotypes with variations in their karyotypic formulae: cytotype I with 12 metacentric, 18 submetacentric, 8 subtelocentric and 14 acrocentric chromosomes with a fundamental number (FN) of 90; cytotype II with 8 metacentric, 28 submetacentric, 6 subtelocentric and 10 acrocentric chromosomes with a fundamental number (FN) of 94. Differences in C- and G-band patterns between the cytotypes, distinguishing marker chromosomes for each karyotype, were reported. The R-band pattern by 5-bromodeoxyuridine incorporation was obtained in chromosomes of the cytotype II sample. In some metaphases, the second pair of submetacentric chromosomes is distinctive: its short arm is heterochromatic (positive C-band), corresponding to a late replication region. In the same cytotype, a G- and R-band size heteromorphism w as recorded in the long arm of pair 9 (submetacentric). These methodologies revealed an actual karyotypic differentiation in the B. aff. iheringii population analyzed. Morphometrical comparative analyses and a discussion of evolutionary aspects of chromosome diversification in species of this genus are provided as well.     

The mobile nature of acrocentric elements illustrated by three unusual chromosome variants

Variant chromosomes are polymorphic in areas that are rich in repeat sequences such as the pericentromeric regions or in the acrocentric short arm regions. The dynamic nature of these regions is evident in the polymorphisms they exhibit. In this paper three unusual variants are described: a chromosome 21 with additional material on its short arm, a chromosome 7 with an insertion in the short arm and a chromosome 2 with satellites at the end of the long arm. All three variants were shown to involve acrocentric elements using special banding techniques and fluorescence in situ hybridization. The 21 variant was found to be a tricentric with a 21 and two 15 alpha-, two classical and three acrocentric beta-satellite signals interspersed by AgNOR-positive regions. The telomeres were present at the two terminal ends. The insertion on chromosome 7 was found to be C-band positive and to contain acrocentric beta-satellite DNA. However, acrocentric alpha-satellite, classical satellite, whole-chromosome-painting or all-telomeres sequence probes did not hybridize to the insertion. The satellited region of chromosome 2 had two C-bands, a small positive all-centromeres probe signal, and two signals for the beta-satellite probe. Sandwiched between the beta-satellite sequences was an AgNOR-positive region. The telomeres were present at the two ends of the satellited chromosome 2. Chromosome 2 subtelomeric probes hybridized to the terminal ends of the short and long arm of chromosome 2. The common thread in these three variants is the involvement of acrocentric short arm elements. The acrocentric short arm elements are shown to move to other acrocentric or nonacrocentric chromosomes and relocate to both terminal and interstitial positions. The integrations are stable and heritable. Received: 23 September 1997 / Accepted: 23 February 1998     

Karyotype of the Snow Sculpin <Emphasis Type="Italic">Myoxocephalus brandti</Emphasis> Steindachner (Cottidae) from Peter the Great Bay,Sea of Japan

The karyotype of the snow sculpin Myoxocephalus brandti, 2n = 44, NF = 46, from Peter the Great Bay was studied. Two-armed chromosomes were presented by one pair of metacentric chromosomes of medium size; one-armed chromosomes included two pairs of large subtelocentric chromosomes and a pair of large acrocentric chromosomes. Ag-NOR-staining in the telomere vicinity revealed nucleolus-organizing regions in one metacentric chromosome and in one medium size acrocentric chromosome in one of the fishes, in two homological small acrocentric chromosomes in three fishes, and in one acrocentric chromosome of average size in six fishes. No difference between the male and female karyotypes and any type of variability was revealed. The karyotypes of the snow sculpin M. brandti and the frog sculpin M. stelleri were compared. Their distinctions and similarities were displayed.Original Russian Text Copyright ¢ 2005 by Biologiya Morya, Ryazanova.     

Chromosomes of lemuriformes. I. A chromosome complement of Lepilemur mustelinus (I. Geoffroy 1851)

The diploid chromosome number of two specimens of Lepilemur mustelinus (I. Geoffroy 1851) is 2N = 20. All of the chromosomes, except the Y chromosome, are metacentric or submetacentric; the Y chromosome is acrocentric and is the shortest chromosome in the complement. Satellites on autosomal pair 5 provide marked chromosomes for the animals studied and may be a marked pair for the species.     

Karyotypes of squirrel monkeys (Saimiri sciureus) from different geographic regions

Three different karyotypes have been found so far among Saimiri originating from five different South American localities. All animals examined have the same diploid number (44) of chromosomes but the number of acrocentric and submetacentric chromosomes varies, presumably as a result of pericentric inversions. Saimiri originating from Iquitos, Peru, consistently have ten acrocentric chromosomes; animals originating from Leticia, Colombia, have 12 acrocentric chromosomes. Hybrids produced in our laboratory have the expected 11 acrocentrics and one unpaired submetacentric chromosome. Animals originating from Guyana have fourteen acrocentric chromosomes and the expected two fewer submetacentric chromosomes. Squirrel monkeys from Costa Rica, Panama, and Pucallpa, Peru, studied to this date conform to the Iquitos type with ten acrocentric chromosomes. These findings point to genetic differences which may result in variable responses to laboratory situations. The evolutionary factors involved in this rearrangement of chromosomes and possible influences on phenotypes are subjects of interest for future study. The importance of identifying the source of squirrel monkeys used in biomedical research is apparent if results from different laboratories are to be repeated or compared.     

Chromosomal banding pattern and idiogram of the cotton rat,Sigmodon arizonae (Rodentia,Muridae)

A procedure for obtaining G-bands on chromosomes of mammals is outlined. The procedure was utilized in an investigation of the idiogram and banding pattern of the mitotic chromosomes of the cotton rat, Sigmodon arizonae. The diploid number of this species is 22, and each pair of homologues is easily separated on the basis of size, centromeric position, and banding pattern. The autosomes are represented by four pairs of large submetacentric chromosomes, three pairs of medium to small submetacentric chromosomes, two pairs of large subtelocentric chromosomes and one pair of small acrocentric chromosomes. The X chromosome is acrocentric and averages from 5.42% to 5.46% of the haploid female complement. The Y chromosome is a minute acrocentric and easily separated from the smallest acrocentric autosome. The usefulnes of Sigmodon arizonae as a laboratory animal for cytogenetic studies is substantiated.     

Synaptonemal complex analysis of heteromorphic trivalents in Lemur hybrids

Synaptonemal complexes (SCs) in surface spread pachytene spermatocytes of Lemur resemble those in other mammals and are of two types: metacentric (or submetacentric) and acrocentric, with a very short second arm. In autosomal SC and mitotic karyotypes of Lemur fulvus (2n=60) a 11 proportionality in relative length is observed as in other mammals. In an intraspecific lemur hybrid (2n=55) obtained by mating L. fulvus rufus (2n=60) x L. fulvus collaris (2n=51), G-band patterns show that 10 single acrocentric mitotic chromosomes correspond to the arms of 5 single metacentrics, implying homology. It is inferred that the metacentrics have evolved by centric (Robertsonian) fusion of the acrocentrics. In the SC karyotype of the hybrid all SCs are normal except for five which have the configurations expected of metacentric-acrocentric trivalents. Similarly, in L. f. collaris (2n= 51), with one unpaired metacentric and two unpaired acrocentrics, one such SC trivalent is present in the complement. In an SC trivalent, each of the acrocentric long axes is synapsed with an arm of the metacentric axis, confirming the homology predicted from banding similarities. At late zygotene, the acrocentric short arms, which are non-homologous, are the last to pair, demonstrating that synapsis of the homologous arms occurs first. At later pachytene the acrocentric short arms are fully synapsed, producing a short SC side arm. This subsequent non-homologous synapsis is taken to be an instance of the synaptic adjustment phenomenon which has been shown to lead to non-homologous synapsis in a duplication and several inversions in the mouse. The kinetochore of the metacentric is the same size as those of the acrocentrics, and thus is unlikely to have arisen by true centromeric fusion, but rather by a translocation. The kinetochores of the acrocentrics always lie together on the same side of the metacentric kinetochore (cis configuration), implying a single pairing face on the metacentric axis. The observed trivalent configuration may well constitute a prerequisite for proper meiotic disjunction in metacentric-acrocentric heterozygotes. Such a mechanism is consistent with fertility regularly observed in such hybrid lemurs.     

Constitutive heterochromatin,G-bands and nucleolus-organizer regions in four species of Didelphidae (Marsupialia)

Chromosomes of Didelphis albiventris, D. marsupialis, Philander opossum and Lutreolina crassicaudata, four species of marsupials with very similar karyotypes and 2n=22 were studied. All the chromosomes were acrocentrics except the X in L. crassicaudata, which is a metacentric.The G-band patterns of these species are similar but the distribution of constitutive heterochromatin differs among them as shown by C-banding. The hypothesis that the X in L. crassicaudata might be an isochromosome derived from the acrocentric X in the other species is discarded since G-and C-banding patterns differ in the two arms.In D. marsupialis the Ag-NORs are terminal and located in both arms of one pair and in the long arms of two pairs of medium-sized autosomes. In P. opossum the NOR-bearing chromosomes could be precisely identified through simultaneous silver staining and G-banding. The Ag-NORs are terminal and located at the short arm of pair 5 and the long arm of pair 7.     

Chromosome number and ploidy-level in a Dutch population ofCrenobia alpina Dana (Planaria)

A Dutch population ofCrenobia alpina was found to have a chromosome number of 2n=42. One pair of large chromosomes is acrocentric and probably shows a secondary constriction; one small pair is acrocentric as well. All other chromosomes are metacentric or sub-metacentric; it has not been possible to discriminate with certainty between them. According to the hypothesis ofDahm (1958) populations with, 2n=42 are autohexaploid, the basic genome consisting of seven chromosomes. On basis of the karyotype it was concluded that the Dutch population described here, is not autohexaploid but functionally diploid, perhaps allohexaploid.     

Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae)

Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, S?o Paulo State, Brazil) were investigated using differential staining techniques (C-banding, Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y1 and Y2 are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.     

Diverse stages of sex-chromosome differentiation in tinamid birds: evidence from crossover analysis in <Emphasis Type="Italic">Eudromia elegans</Emphasis> and <Emphasis Type="Italic">Crypturellus tataupa</Emphasis>

All extant birds share the same sex-chromosome system: ZZ males and ZW females with striking differences in the stages of sex-chromosome differentiation between the primitive palaeognathus ratites and the large majority of avian species grouped within neognaths. Evolutionarily close to ratites is the neotropical order Tinamiformes that has been scarcely explored regarding their ZW pair morphology and constitution. Tinamous, when compared to ratites, constitute a large group among Palaeognathae, therefore, exploring the extent of homology between the Z and W chromosomes in this group might reveal key features on the evolution of the avian sex chromosomes. We mapped MLH1 foci that are crossover markers on pachytene bivalents to determine the size and localization of the homologous region shared by the Z and W chromosomes in two tinamous: Eudromia elegans and Crypturellus tataupa. We found that the homologous (pseudoautosomal) region differ significantly in size between these two species. They both have a single recombination event on the long arm of the acrocentric Z and W chromosomes. However, in E. elegans the pseudoautosomal region occupies one-fourth of the W chromosome, while in C. tataupa it is restricted to the tip of the long arm of the W. The W chromosomes in these two species differ in their heterochromatin content: in E. elegans it shows a terminal euchromatic segment and in C. tataupa is completely heterochromatic. These results show that tinamous have ZW pairs with more diversified stages of differentiation compared to ratites. Finally, the idea that the avian proto-sex chromosomes started to diverge from the end of the long arm towards the centromere of an acrocentric pair is discussed.     

Frequent occurrence of translocations of the short arm of chromosome 15 to other D-group chromosomes

Summary The presence of DA/DAPI (distamycin A/ 4,6-diamino-2-phenyl-indole) heteromorphism on the short arm of human acrocentric chromosomes was investigated in 127 individuals. In 7 cases, a DA/DAPI signal was observed on an acrocentric chromosome other than 15. Subsequently, in situ hybridization (ISH) with a pericentromeric probe specific for chromosome 15 was carried out. In all 7 cases, three ISH signals were present in every metaphase, i.e., on both chromosomes 15 and on the third DA/DAPI-fluorescence-positive acrocentric chromosome (a chromosome 13 or 14), indicating that a chromosome 15 short arm was also present on these chromosomes. Therefore, we conclude that translocations of short arm sequences from chromosome 15 onto other D-group chromosomes occur frequently. Moreover, it appears that DA/DAPI staining remains specific for the short arm of chromosome 15, despite a number of recent papers suggesting otherwise.     

Note on the karyotype and NOR phenotype of leuciscine fish Acanthobrama marmid (Osteichthyes, Cyprinidae)

The karyotype and major ribosomal sites as revealed using silver staining of Anatolian leuciscine cyprinid fish Acanthobrama marmid were studied. The diploid chromosome number was invariably 2n = 50. Karyotype consisted of eight pairs of metacentric, 13 pairs of submetacentric and four pairs of subtelocentric to acrocentric chromosomes. The largest chromosome pair of the complement was subtelo-to acrocentric characteristically, which is a characteristic cytotaxonomic marker for representatives of the cyprinid lineage Leuciscinae. The nucleolar organizer regions (NORs) were detected in the telomeres of two pairs of medium sized submeta-to subtelocentric chromosomes. No heteromorphic sex chromosomes were found. The karyotype pattern of A. marmid is nearly identical to that found in most other representatives of the Eurasian leuciscine cyprinids, while the multiple NOR phenotype appears to be more derived as opposed to a uniform one, ubiquitous in this group.     

Karyotype evolution and geographical distribution of the Thai-medaka, Oryzias minutillus, in Thailand

The karyotype of Oryzias minutillus was examined with specimens collected from 18 localities in Thailand. Specimens from the south and the northeast had 2n = 42 acrocentric chromosomes; the arm number (NF) was 42 and NORs-chromosomes were acrocentric type (2n = 42, NF = 42, NORs-A). Specimens from the central and the north were characteristic by having 8-12 large metacentric chromosomes (LM-chromosomes). They had 2n = 28–34 chromosomes, and shared the same NF and NORs-chromosomes of submetacentric type (2n = 34-28, NF = 44, NORs-SM). Specimens from the southeast had 2n = 42 or 40 chromosomes. Their karyotypes had the same NF and NORs-chromosomes as those from the central and the north (2n = 40–42, NF = 44, NORs-SM), though they had no, or only one pair of, LM-chromosomes. The karyotype with 42 acrocentric chromosomes seems to be basic for O. minutillus , and consequently those with NORs-SM and LM-chromosomes seem to be caused through pericentric inversion and centric fusion, respectively. We confirmed that the karyotype evolution had occurred in drainage areas of the Mae Nam Chao Phraya and collaterals (the central, north and southeast). On the other hand, the basic karyotype was preserved allopatrically in the peninsula (the south) and the basin of the Mae Nam Mun, a tributary of the Mekong (the northeast).     

Karyotype and chromosomal banding pattern in Heteropeza pygmaea

The chromosomes of somatic and germ line cells of female embryos produced by paedogenesis were studied. The haploid set in somatic cells consists of one long submetacentric chromosome, one large acrocentric, one medium metacentric and two small acrocentrics. The length vs arm index karyogram makes it possible to distinguish all but the two pairs of small acrocentric chromosomes. — Attempts were made to develope a method for banding pattern visualization. The best result was obtained using trypsin which induced banding in the chromosomes of the somatic cells and occasionally also of the germ line cells. The resulting banding patterns were frequently not identical in members of a chromosome pair. There was also a variation between metaphases within an embryo as well as from different embryos. Some tentative explanations for these results are discussed.