Showing papers on "Heterochromatin published in 1983"
TL;DR: Analysis of restriction fragments of genomic DNA indicates that the sequences in lambda T-A are homologous to complex sets of repeated sequences that differ from stock to stock in D. melanogaster.
120 citations
TL;DR: The specific effect of 5-azacytidine on the heterochromatin of these chromosomes, its conserving effect on somatic Pairing, and some of the consequences of the somatic pairing on the development of human chromosome aberrations are discussed.
Abstract: Human lymphocyte cultures were treated with different concentrations of 5-azacytidine for various lengths of time. This cytosine analog induces very distinct undercondensation in the heterochromatin o
102 citations
TL;DR: The mitotic and meiotic chromosomes of the marsupial frog Gastrotheca riobambae were analysed with various banding techniques and it is shown that the constitutive heterochromatin in the Y chromosome consists of at least three different structural categories.
Abstract: The mitotic and meiotic chromosomes of the marsupial frog Gastrotheca riobambae were analysed with various banding techniques. The karyotype of this species is distinguished by considerable amounts of constitutive heterochromatin and unusual, heteromorphic XY sex chromosomes. The Y chromosome is considerably larger than the X chromosome and almost completely heterochromatic. The analysis of the banding patterns obtained with GC- and AT-base-pair-specific fluorochromes shows that the constitutive heterochromatin in the Y chromosome consists of at least three different structural categories. The only nucleolus organizer region (NOR) of the karyotype is localized in the short arm of the X chromosome. This causes a sex-specific difference in the number of NOR: female animals have two NORs in diploid cells, male animals one. No cytological indications were found for the inactivation of one of the two X chromosomes in the female cells. In male meiosis, the heteromorphic sex chromosomes form a characteristic sex-bivalent by pairing their telomeres in an end-to-end arrangement. The significance of the XY/XX sex chromosomes of G. riobambae for the study of X-linked genes in Amphibia, the evolution of sex chromosomes and their specific DNA sequences, and the significance of the meiotic process of sex chromosomes are discussed.
96 citations
TL;DR: Since there is evidence to indicate that the size of the distal C-bands has increased subsequent to the introduction of the species into Australia there are good grounds for concluding that this increase has involved the amplification of the highly repeated sequence DNA present within the C- bands.
Abstract: Atractomorpha similis (2 n=19 ♂, 20 ♀) is a hygrophilous, tropical to temperate, species of pyrgomorphine grasshopper. We have sampled 70 populations covering the known distributional range of this species within Australia. All of them proved to be polymorphic for heterochromatin content as revealed by C-band analysis of embryonic neuroblasts. This polymorphism affects all ten members of the basic haploid set and includes variants involving differences in either the presence or the amount of procentric, interstitial and terminal C-blocks, as well as variation in the occurrence and nature of short arms on otherwise telocentric chromosomes. A majority of these variants appear to result from heterochromatin addition since the presumptive sibling, Atractomorpha australis, like other species of the genus that have been C-banded, is generally depauperate in heterochromatin. The net result of this extraordinary polymorphism is that each chromosome of A. similis exists in 10–50 distinct morphs. Consequently, there is a high level of chromosomal heterozygosity in all populations in terms of the number of heterozygous pairs present within a complement and an even higher level in terms of the total range of karyomorph patterns. There is also a wide range of total heterochromatin content, as measured by the percent of the total chromosome area occupied by C-band material, with values ranging from 13% to 44%. Specific marker chromosomes which predominate in particular geographical areas serve to distinguish six major cytotypes within A. similis. The two most southerly of these cytotypes show a narrower range of heterochromatin content but with higher values which reflect the more general occurrence of substantial terminal C-blocks within them. Finally, the populations from Fraser Island constitute a particularly distinctive cytotype characterised by the least number of morphs, the lowest level of chromosomal heterozygosity and a restricted range of heterochromatin content confined to the lower end of the known distributional spectrum.
69 citations
TL;DR: This review describes the existence of a phenomenon, sequential separation of centromeres, in mitotic cells of various species including both animals and plants, and proposes that aneuploidy in humans and other organisms may result from out-of-phase separation of a given chromosome.
61 citations
TL;DR: There appear to be constraints upon changes in nuclear organization during speciation in the evolution of species within the genus Lathyrus.
Abstract: Large changes in chromosome size and nuclear DNA amounts have occurred in the evolution of species within the genusLathyrus, which are also reflected in the amounts of heterochromatin and euchromatin and of repetitive and non-repetitive sequences. The distributions of nuclear DNA in the chromosome complements of 4Lathyrus species are compared. Although there is a doubling of the total amounts of nuclear DNA between highest and lowest of the four species the distribution among the chromosomes of each complement is approximately the same. Hence underlying these evolutionary changes there appear to be constraints upon changes in nuclear organization during speciation.
60 citations
TL;DR: The data suggest that the mutagen-sensitive and repair-defective phenotypes of viable mus-101 mutants result from a disruption in chromosome organization.
Abstract: A temperature-sensitive lethal mutant of Drosophila melanogaster was used to identify an essential cell cycle function that is necessary for the mitotic condensation of heterochromatic but not of euchromatic portions of the genome. This mutant is an allele at a locus (mus-101) identified earlier by the use of mutagen-sensitive mutants. The data suggest that the mutagen-sensitive and repair-defective phenotypes of viable mus-101 mutants result from a disruption in chromosome organization.
57 citations
TL;DR: The fluorescent staining pattern, the electron microscopy, and the enrichment of satellite DNA sequences together support the conclusion that the Eco RI- and Alu I-resistant structures contain centromeres.
Abstract: When L929 cells in metaphase are digested with either Eco RI or Alu I, chromatin containing about 85% of the DNA is released. DNA from the Alu I- and Eco RI-resistant chromatin is enriched 6.8- and 3.7-fold, respectively, in satellite sequences. Analysis by electron microscopy of these digests reveals the existence of structures containing condensed heterochromatin and kinetochores. When these preparations are incubated with anticentromere serum from a human CREST scleroderma patient and then with rhodamine-conjugated antihuman IgG, fluorescence appears in the form of paired dots, the same pattern found in whole metaphase chromosomes. The fluorescent staining pattern, the electron microscopy, and the enrichment of satellite DNA sequences together support the conclusion that the Eco RI- and Alu I-resistant structures contain centromeres. We anticipate that these preparations will be useful in studies of the interactions between centromeric heterochromatin, kinetochores, and microtubules.
51 citations
TL;DR: Quantitatively evaluated C-banding karyograms are presented for Allium carinatum, A.pulchellum, and A. flavum and revealed that constitutive heterochromatin (C-bands) is probably additional chromosomal material.
Abstract: Quantitatively evaluated C-banding karyograms are presented forAllium carinatum, A. carinatum ssp.pulchellum, andA. flavum of the sectionCodonoprasumReichenb. Accurate measurements revealed that constitutive heterochromatin (C-bands) is probably additional chromosomal material. The distribution of the C-heterochromatin follows the principle of the equilocal heterochromatin-distribution byHeitz (1933). Furthermore, the pattern shows a relationship to the relative arm-length of the chromosomes in the karyotype. Fluorochrome banding revealed various heterochromatintypes. The C-band patterns ofAllium cupani (sect.ScorodonKoch) andA. vineale (sect.Allium), which are also rich in heterochromatin, are described.
44 citations
TL;DR: The cytological evidence demonstrates that populations of both species are far from continuous in distribution and the extent to which such cytological differences reflect the existence of subspecific or specific complexes with minimal morphological differentiation is under investigation.
Abstract: Metaphase chromosomes from neuroblasts of strains from both laboratory stocks and natural populations of D. serido, D. meridionalis, D. borborema and D. buzzatii have been studied using colcemid pretreatment, and air-drying followed by Giemsa staining. The two latter species both show a uniform ‘basic’ metaphase karyotype. D. serido and D. meridionalis, on the other hand, both include a number of different, geographically distinct, metaphase karyotypes involving differences in the major blocks of constitutive heterochromatin present on the sex chromosomes and/or the 6th chromosome (microchromosome). These chromosomal differences are largely due to the acquisition of extra heterochromatin though pericentric inversions appear to be responsible for some of the Y-chromosome variants in D. serido. Moreover, the cytological evidence demonstrates that populations of both species are far from continuous in distribution. The extent to which such cytological differences reflect the existence of subspecific or specific complexes with minimal morphological differentiation is under investigation.
40 citations
TL;DR: Great variability of autosomal NOR activity was observed between male individuals and between different tissue of the same male, indicating that this locus escapes sex-chromosome dosage compensation.
Abstract: Somatic and germ cells of the gray short-tailed opossum (Monodelphis domestica) were analyzed cytogenetically by C-banding, G-banding, and silver staining. The diploid chromosome number was found to be 18. C-banding revealed constitutive heterochromatin at the centromeres of all chromosomes, with additional heterochromatin on one arm of the Y. Silver staining for the localization of nucleolus organizer regions (NORs) showed NORs on the X and on a pair of autosomes, tentatively designated as chromosome 5. In females, the NORs on both X chromosomes were active in 98.3% of all somatic cells analyzed, indicating that this locus escapes sex-chromosome dosage compensation. Chromosome 5 showed an active NOR in only 16.2% of cells scored from the six females. In males, 100% of the somatic cells analyzed showed an active NOR on the X chromosome. Greater variability of autosomal NOR activity was observed between male individuals and between different tissues of the same male. Silver staining of pachytene spermatocytes revealed that (1) only an autosomal NOR was active, whereas the NOR of the X chromosome was inactive, and (2) the X and Y chromosomes showed asynaptic behavior, even though all autosomal synaptonemal complexes were fully formed during this stage.
TL;DR: Three suppressor loci for position-effect variegation, one dominant temperature-sensitive (DTS), three Minute genes, and two recessive visible mutants have been cytogenetically localized by using duplicatons and deficiencies in regions 23–25 of chromosome arm 2L of Drosophila melanogaster.
Abstract: Three suppressor loci for position-effect variegation, one dominant temperature-sensitive (DTS), three Minute genes, and two recessive visible mutants (ed, tkv) have been cytogenetically localized by using duplicatons and deficiencies in regions 23–25 of chromosome arm 2L of Drosophila melanogaster. Two of the suppressor loci studied proved to represent haplo-abnormal genes localized in regions 23A6-23F6 and 24E2-25A1, respectively. The third one is a strong triplo-abnormal suppressor mapping in 25F4-26B9 which affects white variegation in wm4h when present in three doses. The l(2)2DTS mutation, which belongs to a group of noncomplementing dominant temperature-sensitive mutations, is localized in the 25A4-B1 region. Furthermore, two Minute genes have been localized in region 24 that are included in Df (2L)M11 and can be separated employing translocation (Y;2)P8 (24E2–4): M(2)LS2 in 24D3-4-24E2-4, and M(2)z in 24E4-5-24F5-7. A third Minute gene (M(2)S1) is localized in 25C3-8-25C9-D1. The usefulness of the isolated chromosomal rearrangements for further genetic studies of region 23–26 is discussed.
TL;DR: Six recombinant DNA clones are described, which are derived from the Y chromosome of Drosophila hydei, and reveal characteristic features of Y chromosomal DNA sequences.
TL;DR: The authors have cloned DNA from the human Y chromosome using fluorescence activated cell sorting and found that at least one single copy sequence is present on both the X and Y chromosomes.
TL;DR: These results suggest that Z-DNA has been conserved during the course of primate evolution and that chromosome homologies previously were demonstrated between these distantly related species by chromosome banding.
Abstract: Antibodies against Z-DNA bind to fixed metaphase chromosomes of man and Cebus albifrons (Platyrrhini, Primate). By indirect immunofluorescence and indirect immunoperoxidase techniques, a heavy staining is detected in some segments of chromosomes of C. albifrons. These segments correspond to R-band-positive heterochromatin, which has a high G + C-base content. Euchromatin of human and Cebus chromosomes show a weak and heterogeneous staining that consistently reproduces an R- and T-banding pattern in both species. Because chromosome homologies previously were demonstrated between these distantly related species by chromosome banding, our results suggest that Z-DNA has been conserved during the course of primate evolution.
TL;DR: DNA, RNA, protein and heterochromatin were measured cytophotometrically in developing soybean (Glycine max) seeds to interpreted that increased DNA levels in soybean cotyledons generated during embryogeny increase the protein synthesizing capacity.
Abstract: DNA, RNA, protein and heterochromatin were measured cytophotometrically in developing soybean (Glycine max) seeds. The average 2C DNA content for the soybean genome was 2.64 pg. The amounts of nuclear DNA in embryo axes showed no significant change during embryo development, whereas the DNA content in cotyledon nuclei increased significantly from 3.58 pg to 5.49 pg. The number of endopolyploid nuclei increased from 26% to 48% and the DNA content from 4.45 to 5.49 pg after cessation of cell division. The changes in RNA and protein content during embryo development were in general similar to those in DNA content. This can be interpreted that increased DNA levels in soybean cotyledons generated during embryogeny increase the protein synthesizing capacity. During the first 15 days of germination, the number of endopolyploid nuclei in cotyledons declined from 46% to 4%, and this decline is interpreted as DNA degradation providing a ready source of nucleosides and phosphates during early embryo growth. A later decline, however, between 15 and 20 days after germination, was age related similar to leaf senescence, because the percentage of endopolyploid nuclei remained unchanged while the number of non-viable cells increased. In senescing cotyledons, 73% and 80% of RNA and protein but only 20% of DNA were lost, as compared to dormant cotyledons. The heterochromatin (condensed chromatin) measurements indicated that nuclei of metabolically inactive dormant and senescent cotyledon nuclei contained an average of 33% more heterochromatin than nuclei from the green cotyledons of seedlings.
TL;DR: Differences in optical retardations in Toluidine Blue-stained material were found and are interpreted as being due to chromatin packing state and selective removal of histones promoted by the acetic acid-ethanol fixative.
Abstract: Two classic cytochemical tests, the Feulgen-Schiff reaction and Toluidine Blue basophilia, have been employed for investigating the differential characteristics of heterochromatin and euchromatin. Differences have been detected in the Feulgen hydrolysis kinetics, the Feulgen absorption spectrum, the image analysis of Feulgen-stained material, and the binding of Toluidine Blue under ordinary and Mg2+ competitive staining conditions. The differences are assumed to be a function of the composition and stereo-arrangement of the DNA and DNA-protein complexes present in these chromatin types and are possibly associated with physiological activities whose whole meaning is far from being clear. Differences in optical retardations in Toluidine Blue-stained material were also found. These are interpreted as being due to chromatin packing state and selective removal of histones promoted by the acetic acid-ethanol fixative.
TL;DR: The pattern of heteromorphisms in the C-band-positive constitutive heterochromatin of human chromosomes No. 1, 9, and 16 was studied in peripheral lymphocytes of patients with soft tissue sarcomas and 78 control individuals.
TL;DR: A technique which permits the simultaneous observation of C-banded material and the active NORs or nucleoli in both mitotic and meiotic chromosomes of mammals and insects is reported.
TL;DR: Analysis of the variability of the C-segment size showed that a correlation with the process of malignant transformation can be sought in the consequences of an uneven distribution and in quantitative changes in the constitutive heterochromatin (chromosomes #1 and #9).
TL;DR: The heterochromatin in the homologous regions of the sex chromosomes allows the formation of a chiasma in the sex bivalent of Chinese hamster spermatocytes, and the heterogeneity found in theseheterochromatic regions may help to establish a more precise relationship between heterochromeatin and recombination.
Abstract: The heterochromatin of the Chinese hamster sex chromosomes was analyzed by different banding techniques. Combined results obtained after differential Ba(OH)2 treatment, BrdU incorporation, Giemsa 11, and staining with quinacrine permitted the characterization of different regions in the heterochromatic portions of the X and Y chromosomes. In the light of these observations, the chiasma observed in the sex bivalent of Chinese hamster spermatocytes was localized within specific heterochromatic regions. The homologous segments consist of the entire short arm of the Y and the distal end of the long arm of the X up to band q21. These regions are probably not rich in highly repetitive DNA sequences, which are more resistant to alkali denaturation, or in satellite DNA, which is stained by Giemsa 11. Thus the heterochromatin in the homologous regions of the sex chromosomes allows the formation of a chiasma. The heterogeneity found in these heterochromatic regions may help to establish a more precise relationship between heterochromatin and recombination.
TL;DR: The role of heterochromatin in homologous pairing and its relationship to chiasma position and number in meiotic configurations were discussed and a comparison was made between bivalent 9 in C. apella and bivalent 21 in man based on the interspecific homologies between these chromosomes.
Abstract: An analysis of the meiotic chromosomes of Cebus apella (Cebidae, Platyrrhini) has allowed for the visualization of constitutive heterochromatic regions throughout the meiotic cycle and has permitted the identification of four chromosomes in the first and the second divisions. In pachytene nuclei, and in pachytene spreads where synaptonemal complexes were visible, one heterochromatic region was frequently unpaired. No chiasmata were found in heterochromatic regions, and there was no evidence of chiasma terminalization. The role of heterochromatin in homologous pairing and its relationship to chiasma position and number in meiotic configurations were discussed. A comparison was made between bivalent 9 in C. apella and bivalent 21 in man, based on the interspecific homologies between these chromosomes. A similar comparison was made between the Algerian and Asian hedgehogs, where marked differences in the content of constitutive heterochromatin occur in two chromosome pairs.
TL;DR: Some reduction of C-segment lengths and their variability on chromsomes 1, 9, 16, and Y was exhibited by children who had had some disturbances at early stages of morphogenesis and the data obtained might suggest a certain activity of the heterochromatic regions during embryo development.
Abstract: Some reduction of C-segment lengths and their variability on chromsomes 1, 9, 16, and Y was exhibited by children who had had some disturbances at early stages of morphogenesis. The data obtained might suggest a certain activity of the heterochromatic regions during embryo development. Based on this data one may also suppose that reduction of the amount of heterochromatin might affect the normal morphogenetic processes.
TL;DR: The heterochromatin is eliminated from the nuclei in many cells during differentiation in the orchidDendrobium as shown by light and electron microscopy, morphometry and scanning cytophotometry.
Abstract: The heterochromatin is eliminated from the nuclei in many cells during differentiation in the orchidDendrobium as shown by light and electron microscopy, morphometry and scanning cytophotometry. The possible significance of this event is briefly discussed, particularly as it relates to heterochromatin underreplication in various organisms.
TL;DR: Evidence is presented that ribosomal gene compensation and nucleolar dominance in polytene cells of Drosophila are separate genetic phenomena, and deletion of the compensatory response (cr(+)) locus does not affect the dominance.
Abstract: Previous studies indicate that genes from only one of the cell's nucleolus organizers undergo multiple rounds of DNA replication in polytene cells of Drosophila. This report presents evidence that this effect is mediated by a function that is associated with the ribosomal genes of the dominant or replicating X chromosome. This function can act in trans to result in replication of the ribosomal genes on the recessive X chromosome in flies that are bobbed for the dominant X chromosome. In these cases, ribosomal genes from both chromosomes undergo polytenization. Heterochromatic regions that flank the nucleolus organizer have little or no effect on nucleolar dominance. In addition, deletion of the compensatory response (cr+) locus does not affect the dominance, suggesting that ribosomal gene compensation and nucleolar dominance in polytene cells of Drosophila are separate genetic phenomena.
TL;DR: Sequences complementary to onager 1.716 g/ml satellite DNA show extensive hybridization to the constitutive heterochromatin of the feral donkey (E. asinus) karyotype, consistent with a view of conservation and amplification of similar or identical sequences in the two species.
Abstract: A (G + C)-rich satellite DNA component (p = 1.716 g/ml) has been fractionated from the total DNA of the Iranian subspecies of the Asiatic wild ass, Equus hemionus onager, by successive dactinomycin-CsCl and netropsin sulfate-CsCl isopycnic gradients. Complementary 3H-RNA (cRNA) transcribed from the satellite DNA hybridized predominantly to the centromeric and telomeric constitutive heterochromatic regions of onager chromosomes. These studies have suggested that satellite DNA's with similar sequences are present in the centromeric, as well as telomeric, heterochromatic regions of some onager chromosomes. The centromeric region of the fusion metacentric t(23;24) of the onager is deficient in sequences homologous to the onager 1.716 g/ml satellite DNA, indicating a loss of satellite DNA during fusion or an amplification of the satellite DNA in the centromeric regions of the acrocentric chromosomes 23 and 24 subsequent to fission. Sequences complementary to onager 1.716 g/ml satellite DNA show extensive hybridization to the constitutive heterochromatin of the feral donkey (E. asinus) karyotype, consistent with a view of conservation and amplification of similar or identical sequences in the two species.
TL;DR: The data presented here suggest strongly M.SM-1 and 2 in R. f.
Abstract: SUMMARYA detailed karyotype comparison among R. cornutus cornutus, R. ferrumequinum nippon and R. luctus formosae are made on the basis of relative length, G- and C-band patterns. The data presented here suggest strongly M.SM-1 and 2 in R. f. nippon were formed by centric fusion of four of five small A-autosome pairs such as those in A-23∼25, 27 and 28 of R. c. cornutus, while occurrence of M-SM-3 in the former was caused by pericentric inversion of a small A-pair such as that in A-24 or 25 of the latter, confirming the assumption described in our previous report (ANDŌ et al. 1980a). On the other hand, appearance of the secondary short arms of A-autosomes in R. f. nippon is attributable to the C-band material added to the telomeres of A-autosomes. Addition of heterochromatin is considered to have taken place also in the short arm of the ST-X chromosome in R. f. nippon, and to have brought about the morphological difference of the Y chromosome within Rinolophus.
TL;DR: It is suggested that the C-heterochromatin plays a "regulatory" role in the population dynamics of this species.
Abstract: Nesokia indica, the Indian mole rat, exhibits extensive variability (polymorphism) for the constitutive heterochromatin of the X and Y chromosomes. These polymorphic X and Y types range from a large metacentric chromosome to a small acrocentric one and occur in different frequencies in the population. On the assumption that there is random mating among individuals carrying these various X and Y chromosomes, the population shows Hardy-Weinberg proportions for the genotypes. However, notwithstanding the partial or total loss of constitutive heterochromatin of the X and Y chromosomes in a few individuals, its retention in most of the animals seems obligatory to the population at large. Hence, we suggest that the C-heterochromatin plays a "regulatory" role in the population dynamics of this species.
TL;DR: The response to hybridization suggests that heterochromatic blocks of chromosome pair VI are heterogeneous in nucleotide sequences, and the present studies indicate that DNA and RNA puffs organized by different chromosome sites are specific of particular steps of embryo differentiation.
Abstract: Different regions of polytene chromosomes pair VI have been characterized by: 1. morphological observations, 2. incorporation of3H-thymidine and3H-uridine, 3. cytophotometry of DNA and associated proteins, 4. hybridization with satellite DNA and highly repeated DNA sequences. The collected data indicate that DNA and RNA puffs are organized by heterochromatic segments. DNA puffs show often a clustered pattern of labeling by3H-thymidine and RNA puffs are always labeled by3H-uridine. Each heterochromatic segment is characterized by a definite ratio between DNA and associated fast-green stainable proteins. Satellite DNA binds mostly to heterochromatic blocks at centromere, highly repeated DNA sequences bind, with approximately the same frequency, to centromeric heterochromatin and to the main intercalary heterochromatic band. The telomeric portions of euchromatin seem to be also enriched in highly repeated DNA sequences. The results indicate that heterochromatic chromosome segments might be sites of intense localized DNA replication. The same chromosome regions are also engaged in an active transcription process. The response to hybridization suggests that heterochromatic blocks of chromosome pair VI are heterogeneous in nucleotide sequences. The present studies also indicate that DNA and RNA puffs organized by different chromosome sites are specific of particular steps of embryo differentiation. The observed metabolic aspects of the suspensors's polytene chromosomes are discussed in relation to the synthesis of growth regulators which is known to occur in the suspensor.