The karyotype,including G- and C-banding patterns,of the pigmy hog Sus (Porcula) salvanius (Suidae,Mammalia)

The diploid chromosome number in the pigmy hog Sus (Porcula) salvanius is 38, the karyotype looking almost identical to that of the domestic pig (S. scrofa) and those wild pigs (S. scrofa) with 2n=38 chromosomes. However, the telocentric chromosomes of the pigmy hog have one or more extra G-bands at, or close to the centromere, and C-bands which are larger than the C-bands in the corresponding chromosomes of the domestic pig.It is argued that the basic chromosome number in the genus Sus is 38 rather than 36. The cytogenetic data are discussed in relation to the taxonomy of the pigmy hog.     

Identification of complexes in a spontaneous triploid Rhoeo spathacea

A ring-of-12 chromosomes at meiosis is characteristic of diploid Rhoeo. Each arm has been assigned a letter in accordance with the segmental interchange theory. Adjacent distribution at anaphase I results in nonviable spores while alternate distribution results in only two types of spores, both viable. Each of these two types has six chromosomes which are collectively either an or a complex. The chromosome complement of a diploid contains one of each. A theoretical diakinesis configuration in the spontaneous triploid Rhoeo is a ring with six bivalents alternating with six univalents. Among the twelve connecting positions, Position D is diagnostic in the triploid. If the complex is in duplicate, two short arms and a long arm are connected at Position D, and Univalent cD is attached to two bivalents by their short arms. In contrast, if the complex is in duplicate, two long arms and a short arm are connected at Position D, and Univalent Dd is attached to two bivalents by their long arms. Squashed preparations of PMC stained with acetocarmine were used. Among a larger number of triploid metaphase I cells studied, 53 had identifiable chromosomes. In four of the 53, all 18 chromosomes were identified. Chiasma failures in these four PMC were distributed at random among the 12 positions, and at random relative to arm length. The unique features predicted in the presence of an extra complex were observed. Root tip karyotypes had only four (rather than five) large metacentrics. It is concluded that the chromosome complement of the triploid consists of two complexes and one complex. Implications for the balanced lethal mechanism are discussed.This paper represents part of a dissertation submitted in partial fulfillment of the requirements for a Ph. D. degree in genetics at The Ohio State University, Columbus, Ohio, USA.     

C-heterochromatin variation in the genus Eumigus (Orthoptera: Pamphagoidea)

Eumigus punctatus, E. monticulus and E. cucullatus all have 2n=19 and similar chromosome morphology, all the elements being telocentric. In E. cucullatus there are C-bands in all chromosomes, but not in E. monticulus. The possible origins of these differences and their cytotaxonomic significance are discussed.     

Chromosome alterations in the karyotype of triticale in comparison with the parental forms

Summary R genome chromosomes were studied in two forms of primary triticales (hexaploid TPG-1/1-78 and octoploid AD 825) and in their parent rye forms (Secale cereale L. cv. Kharkovskaya 60 and VSKhI, respectively) using the methods of C-banding and morphometric analysis. The size of some heterochromatic segments was shown to alter in the karyotype of triticale. An increase in size was detected approximately in half of all telomeric C-bands; the size of the other C-bands either decreased or did not change. The frequencies of these alterations were 11. The variability in the size of telomeric C-bands in rye chromosomes diminished in both triticales studied. The two triticale forms inherited variants of R genome chromosome polymorphism predominantly with the medium size range of telomeric C-bands. The centromeric C-bands in both triticale forms either enlarged or did not alter. Possible mechanisms responsible for the observed pattern of alterations are discussed.     

Characterization of heterochromatin in Schistocerca gregaria by C- and N-banding methods

Mitotic and meiotic chromosomes of Schistocerca gregaria were C-, mild N- and strong N-banded. After C-banding, three out of eleven autosomes show, in addition to the centromeric C-bands, a second C-band. — The mild N-banding method produces a single N-band in each of only four chromosomes. With the exception of one N-band these mild N-bands correspond to the non-centromeric, second C-bands, indicating the heterochromatic character of at least three mild N-band regions. — The strong N-banding technique produces bands both at the C- and mild N-band positions and additionally a third band in one chromosome (M₈), not present after C- or mild N-banding. — The N-bands do not correspond to the nucleolus organizer regions. Because of the mechanisms of the N-banding methods, it is concluded that the centromeric heterochromatin, as well as the non-centromeric N-band regions, contain high quantities of non-histone proteins. Presumably a specific difference exists between the non-histone proteins in the centromeric and non-centromeric N-band regions because the centromeres are banded by the strong N-banding technique, but not after mild N-banding. It is concluded that the N-band regions (two exceptions) contain a heterochromatin type which has the following features in common with the -heterochromatin of Drosophila: C- as well as N-banding positive, high nonhistone protein content, repetitive and late replicating DNA. It is discussed whether the N-banded heterochromatin regions of Schistocerca contain that DNA fraction which is, like the Drosophila -heterochromatin, underreplicated in polyploid nuclei.     

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.Considering the male meiotic characteristics, the chromosome complement and the results of C-banding and DNA content, the karyotype of B. oxyurum probably originated through autosomal fusions. The karyotype of B. micantulum and B. elegans could have originated through autosomal fusions or fragmentations respectively; with the information available up to now it is not possible to discard any of the two pathways.     

Identification of Haynaldia villosa chromosomes added to wheat using a sequential C-banding and genomic in situ hybridization technique

Genomic in situ hybridization (GISH) offers a convenient and effective method for cytological detection, but can not determine the identity of the chromosomes involved. We integrated C-banding with GISH to identify Haynaldia villosa chromosomes in a wheat background. All chromosomes of H. villosa showed C-bands, either in telomeric regions or in both telomeric and centromeric regions, which allowed unequivocal identification of each H. villosa chromosome. The seven pairs of H. villosa chromosomes were differentiated as 1–7 according to their characteristic C-bands. Using a sequential C-banding and GISH technique, we have analyzed somatic cells of F₃ plants from the amphiploid Triticum aestivum-H. villosa x Yangmai 158 hybrids. Three plants (94009/5-4,94009/5-8 and 94009/5-9) were shown to contain H. villosa chromosome(s). 94009/5-4 (2n = 45) had three H. villosa chromosomes (2, 3 and 4); 94009/5-8 (2n = 45) possessed one chromosome 4 and a pair of chromosome 5, and 94009/5-9 (2n = 43) was found to have one chromosome 6 of H. villosa. The combination of GISH with C-banding described here provides a direct comparison of the cytological and molecular landmarks. Such a technique is particularly useful for identifying and localizing alien chromatin and DNA sequences in plants.     

Comparative chromosomal studies on two minnow fish, Phoxinus phoxinus (Linnaeus, 1758) and Eupallasella perenurus (Pallas, 1814); an associated cytogenetic-taxonomic considerations

The present work provides new data on the banding pattern of two cyprinid fish species Phoxinus phoxinus and Eupallasella perenurus from Poland. C-banding, silver-staining (Ag), and fluorescent staining with chromomycin A₃ techniques were used to describe the karyotypes. Both of the species karyotypes of 2n=50 were characterised by one pair of acrocentric chromosomes, the largest in the set, and by two pairs of NOR-bearing chromosomes. In the chromosome set of Ph. phoxinus Ag-stained NORs were located on telomeres of two metacentric and two submetacentric chromosomes, but in most metaphases only one of the two homologous was observed. The karyotype of E. perenurus was characterised by Ag-NOR regions at a telomeric position on the shorter arm of two submetacentric chromosome pairs. In most metaphases only three NOR-bearing chromosomes were observed. In both investigated species the location of the A₃ positive signals corresponded with the location of Ag-stained NORs and these sites were associated with heterochromatin shown as C-bands. The results of cytogenetical studies on other related, mainly the North American phoxinins, species are compared and discussed.     

Quantitative analyses of C-banded karyotypes,and systematics in the cultivated species of theScilla siberica group (Liliaceae)

Quantified C-band karyograms are presented for the related speciesScilla siberica, S. mordakiae, S. ingridae, S. amoena, andS. mischtschenkoana. Chromosome structure, banding style, and heterochromatin characters suggest a systematic grouping of two more closely related species pairs:S. siberica andS. mordakiae, S. ingridae andS. amoena; they are part of a larger aggregate, well separated fromS. mischtschenkoana. Four different heterochromatin fractions can be recognized inS. siberica and its relatives, but only two inS. mischtschenkoana. C-bands do not replace, but they are added to euchromatin. The particular origin and history of the cultivatedS. amoena and the triploidS. siberica cv. Spring Beauty appear to be responsible for their karyotype constancy, but chromosome conservatism obviously is genuine inS. mischtschenkoana. The banding data support the systematic grouping proposed on a morphological basis, and provide additional evolutionary evidence.Evolution ofScilla and Related Genera, IV.     

Analysis of chromatin-associated fiber arrays

The distribution of constitutive heterochromatin has been investigated in four chromosomal races of the grasshopper Caledia captiva (2n= 23 /24 ) by the C-banding technique. Each of the four races was found to have a distinctive banding pattern which is associated with the inter-racial differences in chromosomal rearrangements. — The Ancestral race has a telocentric chromosome complement with large procentric C-bands which are structurally double on six pairs of chromosomes. The centromeres are unstained. — The General Purpose race has a C-banding pattern very similar to that seen in other Acridine grasshoppers with the majority of its chromosomes showing a centromeric localisation of the bands. — The two southern races, which show a complex polymorphism for presumed pericentric inversions on all twelve chromosomes, also show an unusually high level of interstitial and terminal C-bands. The different locations and numbers of these bands allow unambiguous identification of all the chromosome pairs within the complement. — In two cases, there is good evidence to indicate that a C-band redistribution between acrocentric and metacentric chromosomes has occurred by pericentric inversion. Furthermore, C-band variation on the long arm of the metacentric X-chromosome indicates the presence of a large paracentric inversion. This double inversion system has involved over 95% of the X-chromosome. — The interstitial and terminal C-bands probably have not resulted from heterochromatin movement within the complement but, more likely, have arisen by saltatory duplication of pre-existing sequences on the chromosome. — A new nomenclature system for banded chromosomes is proposed which allows most kinds of chromosomal restructuring and rearrangement to be adequately enumerated.     

Cytogenetics of the parthenogenetic grasshopper Warramaba virgo and its bisexual relatives

A study of the chromosomal location and genomic organization of the ribosomal RNA cistrons in the genus Warramaba, involving in situ hybridization and restriction enzyme analysis as well as C- and N-banding and silver staining, has confirmed that the parthenogenetic species W. virgo has two phylads. These phylads appear to have originated independently by hybridization between the precursors of the present day bisexual species P169 and P196. The clones of the Standard phylad of W. virgo have their 18S+26S rDNA cistrons located in C-bands 4, 44 and 49, while those of the Boulder-Zanthus phylad have them in C-bands 50, 74 and 87.5. The relative numbers of the ribosomal genes at the different sites vary greatly from clone to clone and are closely correlated with the width of the corresponding C- and N-bands. Site 49 of the ribosomal cistrons is present as a separate band in the eastern race A of P196 but has been incorporated into band 50 in the western race B of this species. The former race is assumed to be ancestral to the Standard phylad of W. virgo, the latter to the Boulder-Zanthus phylad, but there has been loss of the 74 and 87.5 sites in the the Standard phylad and the 4 and 44 sites in the Boulder-Zanthus clones. The ribosomal cistrons in W. picta, a species with a primitive karyotype, occur in several sites, only some of which have counterparts in P169 and P196. The 5S rDNA cistrons are located in bands 59.5, 69 and 72.5 in the Standard phylad of W. virgo. — The genomic organization of the 18S+26S rDNA cistrons, as shown by restriction enzyme analysis, is different in the two W. virgo phylads and there are also differences in organization between P196A and P196B. The pattern in P196B and that in the Boulder-Zanthus phylad suggest that they are related. As in the in situ analyses, the genomic organizations of the ribosomal cistrons in both W. virgo phylads are not simply the additive products of those in any known populations of P169 and P196. New repeat lengths indicative of segmental amplification events occur in particular clones of W. virgo. — Throughout the genus Warramaba the N-banding technique stains all bands containing 18S+26S and 5S rDNA cistrons. The Olert silver technique stains band 72.5 in the Standard phylad, but does not correlate with the locations of 18S+26S ribosomal genes.     

Identification of Renner complexes and duplications in permanent hybrids of Gibasis pulchella (Commelinaceae)

Discovery of permanent hybridity in the very large chromosomes of Gibasis pulchella (Commelinaceae) has allowed specific identification of segmental interchanges in complex heterozygotes. The interchanges are confined to terminal regions, are sometimes very small, and may be unequal in size. Breakpoints have occurred close to major C-bands, probably at euchromatin/heterochromatin boundaries. Complete and disjunctional ring formation at meiosis results in the segregation of two Renner complexes, each of which can be specifically identified with C-banding. The complex carrying the interchanges is usually transmitted through the pollen. Certain chromosomes that have undergone more extensive change than the rest of the complement may have some special significance. There is evidence of small duplications within heterozygous genomes. Permanent hybridity in different organisms may have quite different origins, possibly initiated by major karyotype repatterning following the activation of transposons that generate chromosome breakage.Abbreviations p Short arm - q long arm - M metacentric - SM submetacentric - BS bisatellited chromosome in population 4 - UB unbanded chromosome in population 4 - II bivalent; closed meiotic ring configuration, e.g., 10, ring of ten - ch open chain configuration - NOR nucleolus organising region     

Mapping of genes controlling seed storage-proteins and cytological markers on chromosome 1R of rye

Summary Rye secalins, telomeric C-bands, and telocentric chromosomes were used as markers in the progeny of a test-cross in order to determine the position of seed storage-protein genes Glu-R1 and Gli-R1 with respect to the centromere and both telomeres of chromosome 1 R in rye. These genes were linked to the centromere (32.35±3.28% and 36.27±3.37% recombination, respectively). Glu-R1 was loosely linked to the telomere of the long arm (43.63±3.47% recombination), while Gli-R1 was closely linked to the telomere of the short arm (9.80±2.08% recombination). This finding supports the possibility that rye - and -secalin genes may be located on the satellites, as has been described in wheat for genes that code similar proteins. The importance of metaphase-I pairing failure and its consequences for the estimation of the recombination fraction are also discussed.     

Chromosome polymorphism in the Italian newt,Triturus italicus

A chromosomal variation, changing shape and C-banding pattern of chromosome XII of Triturus italicus was detected among the offspring of two F₁ hybrid families of T. italicus × T. vulgaris meridionalis . In both families a number of individuals appeared to have a metacentric instead of the expected subtelocentric chromosome XII of T. italicus. — Investigations in three well separated localities in the range of the species showed the polymorphism to have a wide distribution and to be part of a complex pattern involving at least two inversions and (presumably) deficiencies of large C-bands. At meiosis, the shape of bivalent XII, and the location and frequency of chiasmata in the bivalent varied with the karyomorph involved. It is suggested that large rearrangements may still play an important role in the karyological evolution of Triturus.     

Variation in nuclear DNA in the genus Secale

Estimates of the 4C DNA amount per nucleus in 16 taxa of the genus Secale made by Feulgen microdensitometry ranged from 28.85 picograms (pg) in S. silvestre PBI R52 to 34.58 pg in S. vavilovii UM 2D49, compared with 33.14 pg in S. cereale cv. Petkus Spring which was used as a standard. Giemsa C-banding patterns showed considerable interspecific and intraspecific variation and several instances of polymorphism for large telomeric C-bands. The proportion of telomeric heterochromatin in the genome ranged from about 6% in S. silvestre and S. africanum to about 12% in cultivated rye. A detailed comparison of nine taxa showed no overall relationship between 4C DNA amount and the proportion of telomeric heterochromatin in the genome. However, evidence is presented which strongly supports the notion that the major evolutionary change in chromosome structure in Secale has involved the addition of heterochromatin at, or close to, the telomeres. It is suggested that saltatory amplification events at telomeres were initially responsible for each large increase in DNA amount. Subsequently unequal crossing over between homologues may have played an important secondary role by extending the range of variation in the amount of heterochromatin at a given telomere, while crossing over between non-homologues may have provided a useful mechanism allowing an increase in the DNA amount at one telomere to be distributed between chromosomes.     

Chromosome banding in amphibia

In the chromosomes of 12 frog species of the suborder Diplasiocoela (Amphibia, Anura), the constitutive heterochromatin and the nucleolus organizer regions (NORs) have been specifically stained. On most of the chromosomes, aside from the centric heterochromatin, telomeric and interstitial C-bands were also found. The various C-bands display a very variable reaction to alkaline pretreatment; this indicates heterogeneity in the constitutive heterochromatin. Sex chromosomes could not be identified in any of the species studied. The number and chromosomal positions of the NORs vary quite strongly between species and between families. In 4 species of the genus Rana, there were, aside from the standard-NORs in chromosome pair 10, between 4 and 14 extra, small NORs detectable in the smaller chromosome pairs. As possible causal mechanism of these additional small NORs the reintegration of amplified rDNA during amphibian oogenesis is suggested. Q- or G-bands could only be recognized in mitotic prophase chromosomes. The strong spiralization of metaphase chromosomes prevents the differential demonstration of Q- or G-bands in the euchromatic regions.     

Multiplication of 28S rDNA and NOR activity in chromosome evolution among ants of the Myrmecia pilosula species complex

Chromosomal localization of rDNA in samples of five taxa of the Myrmecia pilosula species complex (Hymeoptera: Formicidae: Myrmeciinae) with 2n=3 (M. croslandi), 8 (M. imaii), 10 (M. banksi), 18 (M. haskinsorum), and 27 (M. pilosula) was carried out by fluorescence in situ hybridization (FISH) using cloned M. croslandi rDNA (pMc.r2) including the coding region for 28S rRNA. Results show that (1) the 28S rDNA in the genome of these ants is repetitive and is localized in pericentromeric C-bands, (2) the number of chromosomes carrying rDNA is two in M. croslandi, M. imaii and M. banksi, six in M. haskinsorum and ten in M. pilosula, and (3) only one or two clusters of rRNA genes generate nucleoli in each species. We suggest that the rDNA in the ancestral stock of the M. pilosula complex was localized originally in a pericentromeric C-band, and multiplied by chance with time during saltatory increases in C-banding following episodes of centric fission. Most rDNA multiplied on various chromosomes seems to be inactivated and eliminated from the genome, together with C-bands, by -inversion or centric fusion, with the remnant rDNAs dispersed in the genome by centric fission and -inversion.     

C-banding pattern and polymorphism of Aegilops caudata and chromosomal constitutions of the amphiploid T. aestivum — Ae. caudata and six derived chromosome addition lines

Summary C-banding patterns were analysed in 19 different accessions of Aegilops caudata (= Ae. markgrafii, = Triticum dichasians) (2n = 14, genomically CC) from Turkey, Greece and the USSR, and a generalized C-banded karyotype was established. Chromosome specific C-bands are present in all C-genome chromosomes, allowing the identification of each of the seven chromosome pairs. While only minor variations in the C-banding pattern was observed within the accessions, a large amount of polymorphic variation was found between different accessions. C-banding analysis was carried out to identify Ae. caudata chromosomes in the amphiploid Triticum aestivum cv Alcedo — Ae. caudata and in six derived chromosome addition lines. The results show that the amphiploid carries the complete Ae. Caudate chromosome complement and that the addition lines I, II, III, IV, V and VIII carry the Ae. caudata chromosome pairs B, C, D, F, E and G, respectively. One of the two SAT chromosome pairs (A) is missing from the set. C-banding patterns of the added Ae. caudata chromosomes are identical to those present in the ancestor species, indicating that these chromosomes are not structurally rearranged. The results are discussed with respect to the homoeologous relationships of the Ae. caudata chromosomes.     

Counterstained enhancement of TaqI resistant sites after distamycin A/diamidinophenylindole treatment

Numerous selective and differential staining techniques have been used to investigate the hierarchical organisation of the human genome. This investigation demonstrates the unique characteristics that are produced on fixed human chromosomes when sequential procedures involving restriction endonuclease TaqI, distamycin A (DA) and 4,6-diamidino-2-phenylindole (DAPI) are employed. TaqI produces extensive gaps in the heterochromatic regions associated with satellite II and III DNAs of human chromosomes 1, 9, 15, 16 and Y. DA/DAPI selectively highlights, as brightly fluorescent C-bands, the heterochromatin associated with the alpha, beta, satellite II and III DNAs of these chromosomes. When DA and DAPI are used on chromosomes before TaqI digestion, and then stained with Giemsa, the centromeric regions appear to be more resistant, producing a distinct C-banding pattern and gaps in the heterochromatin regions. Sequential use of the DA/DAPI technique after TaqI treatment produces a bright fluorescence on the remaining pericentromeric regions of chromosomes 1, 9, 16 and Y, which also displayed a cytochemically unique banding pattern. This approach has produced specific enhanced chromosomal bands, which may serve as tools to characterize genomic heterochromatin at a fundamental level.     

Experimental hybridization within the genus Triturus (Urodela: Salamandridae)

Spermatogenesis in the F₁ hybrid (2n=24=12 +12 ) between the closely related newt species T. cristatus carnifex and T. marmoratus was apparently normal up to pachytene. Many unpaired chromosomes were present at diplotene and a typical diakinesis was lacking. Primary spermatocytes at meta-and meta-anaphase contained up to 12 regular intergenomal bivalents and a corresponding number of univalents when less then 12 II. Most chiasmata were terminal or subterminal, some intercalary. Chiasmata between corresponding heterospecific chromosomes can be reported as true: real crossing over has taken place, proving the presence of primary chromosomal homologies between the 2 sets of the parental species. Evidence for recombination is based on the segregation of particular markers (i.e., subterminal C-bands and NORs) observed in certain chromosomes at metaphase II. One chromatid of single chromosomes can show the T. cristatus phenotype and the other the T. marmoratus phenotype. A few primary spermatocytes contain a certain number of irregular associations (intragenomal or intrahaploid bivalents, irregular intergenomal bivalents, chromosome multivalents) joined by chiasmata which can be defined as anomalous. Other abnormalities concern the occurrence of interlocked bivalents which occasionally show an anomalous exchange between heterologous chromatids. — Cytogenetic criteria useful to evaluate the taxonomic relationships between different species have been discussed as well as some possible trends in chromosome evolution and speciation within the genus Triturus.