Showing papers on "Heterochromatin published in 1974"
TL;DR: The chromosomes of rye have been individually identified by their distinctive heterochromatin pattern with Giemsa staining and classified on the basis of their homoeology with wheat chromosomes.
Abstract: The chromosomes of rye have been individually identified by their distinctive heterochromatin pattern with Giemsa staining and classified on the basis of their homoeology with wheat chromosomes. The constitutive heterochromatin detected by C-banding has been shown to be identical with the classical heterochromatin as seen in the pachytene of meiosis in rye.
137 citations
Journal Article•
111 citations
TL;DR: The behavior of heterochromatin during premature chromosome condensation (PCC) was studied in a cell line of Microtus agrestis after fusion with mitotic HeLa cells.
Abstract: The behaviour of heterochromatin during premature chromosome condensation (PCC) was studied in a cell line of Microtus agrestis after fusion with mitotic HeLa cells. In the G1- and G2-PCC, the heterochromatic nature of the X-chromosomes was detectable by their intense staining. The pulverized appearance of the S-phase PCC was correlated with incorporation of 3H TdR into the DNA. Three types of S-PCC were observed. PCC with a pulverized appearance of: (a) only the autosomes (early S); (b) autosomes and X-chromosomes (mid S); and (c) only the X-chromosomes (late S). The behaviour of heterochromatin during replication, as observed by the PCC method, was no different from that of euchromatin. The data on the sequence of chromosome replication indicate that the centromeric regions of the X-chromosomes were the last segments to replicate. The completion of DNA synthesis in the X-chromosomes appears to be followed by progressive chromosome condensation during G2 even before the actual initiation of prophase.
107 citations
TL;DR: Portions of constitutive heterochromatin of the Chinese hamster Cricetulus griseus, do not appear to contain a disproportionately high amount of repeated DNA sequences.
Abstract: Portions of constitutive heterochromatin of the Chinese hamster Cricetulus griseus, do not appear to contain a disproportionately high amount of repeated DNA sequences. These specific regions are the long arm of the X chromosome, the entire Y chromosome, and the centromeric region of chromosome 10. Other heterochromatic areas of the Chinese hamster chromosomes showed localization of repetitious DNA.
83 citations
TL;DR: It is considered that «inert heterochromatin is in fact an active entity» and the possibility of achieving a specificity of interaction with macromolecules not based on variations of their structure, namely «distributive specificity, is pointed out.
72 citations
TL;DR: Rye chromosomes were selectively stained in the meiosis of triticale by means of heterochromatin banding techniques and showed reduced pairing at first meiotic metaphase, which could arise from an overlap between the processes of chromosome replication and chromosome pairing.
Abstract: Rye chromosomes were selectively stained in the meiosis of triticale by means of heterochromatin banding techniques. Compared to wheat chromosomes, rye chromosomes showed reduced pairing at first meiotic metaphase. Within the rye genome this pairing failure was associated with the presence of large, terminal heterochromatic bands. Since these terminal bands of rye chromosomes are late replicating, the effect of heterochromatin could arise from an overlap between the processes of chromosome replication and chromosome pairing.
69 citations
TL;DR: A comparison of the Giemsa-banding patterns of the X chromosomes in various mammalian species including man indicates that two major bands (A and B), which are resistant to trypsin and urea-treatments, are always present irrespective of the gross morphology of theX chromosomes.
Abstract: A comparison of the Giemsa-banding patterns of the X chromosomes in various mammalian species including man indicates that two major bands (A and B), which are resistant to trypsin and urea-treatments, are always present irrespective of the gross morphology of the X chromosomes. This is true in all mammalian species with the "original or standard type" X chromosomes (5–6% of the haploid genome) thus far analyzed. In the unusually large-sized X chromosomes the extra chromosomal material may be due either to the addition of genetically inert constitutive heterochromatin or to an X-autosome translocation. In these X chromosomes two major bands are present in the actual X-chromosome segment. Our data on C and G band patterns also support Ohno's hypothesis that the mammalian X chromosome is extremely conservative in its genetic content, in spite of its cytogenetic variability.
68 citations
TL;DR: The “uncoiler” heterochromatic region is much more susceptible to the BUdR action than the telomeric regions, the exchange rates being doubled and this agrees with the higher incidence of morphological alterations such as extension and structural loosening in this region.
Abstract: SummaryAfter incorporation of the base analogue 5-bromodeoxyuridine (BUdR) into PHA activated human lymphocyte cultures and subsequent staining with the benzimidazol compound “33258 Hoechst” and with Giemsa stain, the sister chromatids of metaphase chromosomes are stained differently in the 2nd and 3rd cycle of cell division.The first mitosis appears after culturing for 30 hrs. The 2nd and the 3rd metaphase generation appear at about 66 and 72 hrs after activation respectively. In 72-hour cultures three cell generations are found at the same time. Consequently this culture time is not adequate for scoring chromosome aberrations induced by mutagenic agents.Chromatid exchange is frequently visible predominantly in the 2nd cell generation, averaging 14 exchanges (range 4–35) per metaphase.The “uncoiler” heterochromatic region is much more susceptible to the BUdR action than the telomeric regions, the exchange rates being doubled. This agrees with the higher incidence of morphological alterations such as extension and structural loosening in this region. Nevertheless, it is notable that this area does not break very frequently.After treatment with Trypsin and Giemsa the banding pattern can be seen in both chromatids labelled with BUdR.
63 citations
TL;DR: Differential Giemsa staining techniques have been used to stain kinetochores and nucleolus organizer heterochromatin in four species of higher plants and have allowed the determination of the number and sites of nucleolUS organizers in the various chromosome complements studied.
Abstract: Differential Giemsa staining techniques have been used to stain kinetochores and nucleolus organizer heterochromatin in four species of higher plants. Using these techniques it has been possible to follow developmental changes of kinetochores through mitosis. In addition, these same techniques also have allowed the determination of the number and sites of nucleolus organizers in the various chromosome complements studied.
60 citations
01 Jan 1974
55 citations
TL;DR: It is suggested that the two types of particles seen in the β-heterochromatin are products of RNA synthesis occurring in this region, which raises doubts on the general validity of the notion of total inactivity of constitutive heterochromaatin.
TL;DR: The heterochromatin patterns of three mammalian species are presented to demonstrate that within each karyotype there may be several different types of C bands.
Abstract: The constitutive heterochromatin, as demonstrated by the C band technique, may be subdivided into a number of categories when other characteristics are considered. The responses to fluorochromes QM and 33258 Hoechst, the behavior following G band staining, the repetitive DNA content, and many other criteria are useful for the classification of heterochromatin. The heterochromatin patterns of three mammalian species are presented to demonstrate that within each karyotype there may be several different types of C bands. In general, a correlation may also be made between GC-rich satellite DNA and dull (or negative) Q fluorescence, and between AT-rich satellite DNA and bright Q, fluorescence.
TL;DR: The Giemsa-stained C-bands account for all the heterochromatin in rye nuclei, including metaphase chromosomes within the complement, as revealed by Feulgen staining.
Abstract: C-banding, by Giemsa staining, is largely restricted to distal regions of rye chromosomes. This applies, also, to B chromosomes. The distribution of C-bands coincides with that of distally localised heterochromatin. The area of metaphase chromosomes staining with Giemsa corresponds to the area occupied by heterochromatin in interphase nuclei as revealed by Feulgen staining. The Giemsa-stained C-bands account, therefore, for all the heterochromatin in rye nuclei. Individual chromosomes within the complement are readily identified following Giemsa staining.
TL;DR: In the nuclei of salivary glands of individuals with extreme variegation the transposed 1A3-4-3A1-2 region of the polytene X- Chromosome has an altered (heterochromatinized) morphology as compared to the homologous interval of the normal X-chromosome.
Abstract: Variegated position-effect in Drosophila melanogaster was studied using the chromosomal rearrangement Dp (1;f) R, which is a transposition of the euchromatic region 1A3-4-3A1-2 of the X-chromosome to centromeric heterochromatin of the same chromosome. The transposition shows variegation for dor+ and adjacent genes and results in the appearance of non-pigmented cells in the yellow Malpighian tubules of variegated larvae. Variegation is drastically enhanced by the elimination of the Y chromosome and the decrease of rearing temperature. — In the nuclei of salivary glands of individuals with extreme variegation the transposed 1A3-4-3A1-2 region of the polytene X-chromosome has an altered (heterochromatinized) morphology as compared to the homologous interval of the normal X-chromosome. Heterochromatinization consists in the elimination of several bands, the appearance of unusually dense bands, absence of puffs and weakening of the conjugation of chromatids. — Autoradiographic studies with polytene chromosomes after pulse labelling with 3H-thymidine and 3H-uridine reveal that both transcription and replication in the transposed region are altered in larvae showing extreme variegation. The alterations consists in a 40% decrease of RNA synthesis and a delay of replication in the transposed region. Long-term labelling with 3H-thymidine reveals an underreplication of DNA in the transposed euchromatin which is most pronounced in the regions adjacent to heterochromatin. The delay of replication and underreplication of euchromatin resulting from transposition to heterochromatin may be the cause of eventual inactivation of genes in the transposed region.
TL;DR: It is suggested that low DNA content and short cycles might be factors determining the generation time of short-lived plants, and these assumptions fit the general findings that DNA contents have increased strikingly during general evolution but have decreased during specialisation.
Abstract: RECENTLY Bennett has demonstrated that most annual plants have less nuclear DNA than perennial plants1. Since there is a positive correlation between DNA content and minimum duration of the mitotic cell cycle2, Bennett suggested that low DNA content and short cycles might be factors determining the generation time of short-lived plants. These assumptions also fit the general findings that DNA contents have increased strikingly during general evolution3 but have decreased during specialisation4–6.
TL;DR: The DNA from several Anemone species, which contain different amounts of heterochromatin as revealed by Giemsa staining, was analysed by ultra-centrifugation and renaturation and showed the presence of repetitive sequences.
Abstract: The DNA from several Anemone species, which contain different amounts of heterochromatin as revealed by Giemsa staining, was analysed by ultra-centrifugation and renaturation. No satellite band was observed in any of the samples centrifuged in cesium chloride gradients. Renaturation studies showed the presence of repetitive sequences. The proportion of repetitive DNA per genome varied from 53% to 67% and did not correlate with either the DNA content per cell or the relative amount of heterochromatin.
TL;DR: The sequence of chromosome replication and the extent of RNA transcription were determined for pre-meiotic S-phase and first meiotic prophase in males of Myrmeleotettix maculatus and Chorthippus parallelus and these findings are discussed in relation to the definition of heterochromatin.
Abstract: The sequence of chromosome replication and the extent of RNA transcription were determined for pre-meiotic S-phase and first meiotic prophase in males of Myrmeleotettix maculatus and Chorthippus parallelus. Some heterochromatic chromosome segments are replicated early in S-phase while others are replicated late. In general, heavily condensed heterochromatic regions of the chromosomes show little or no RNA transcription as defined by 3H-uridine incorporation. Extra (i.e. in excess of 2) M4 autosomes in Ch. parallelus are slightly more condensed (heterochromatic) than their two homologues and this change in coiling behaviour is paralleled by a reduction in the rate of transcription and a change in the time of its replication, more of the DNA being synthesised at the end of S-phase. These findings are discussed in relation to the definition of heterochromatin.
TL;DR: Soluble chromatin contains short protein-rich regions, the function of which is unknown at present, and is incompatible with the two fractions being heterochromatin and euchromatin, as these are usually defined.
TL;DR: Centromeric heterohromatin as revealed by the Giemsa BSG technique has been quantitatively analyzed in giant versus diploid trophoblast nuclei, and a constant ratio of chromocenter area: total nuclear area in giant cells is observed.
Abstract: Giant trophoblast nuclei of the mouse and the rat, known to contain hundreds, or even thousands, of times the haploid amount of DNA, have been studied by a number of cytological techniques. These nuclei appear in two morphological states:“reticulate,” in which large numbers of chromatin threads of uniform size intermingle throughout the nucleus, often radiating from clumps of heterochromatin adjacent to the nucleoli, and “homogeneous,” in which the chromatin is more evenly dispersed and individual threads are more difficult to distinguish. Intermediate morphologies are also observed. In neither case were structures resembling polytene chromosomes discernible. — Centromeric heterohromatin as revealed by the Giemsa BSG technique has been quantitatively analyzed in giant versus diploid trophoblast nuclei. Although the median number of chromocenters is slightly greater in giant than in diploid nuclei, the range is similar. In both cases, the chromocenter number is usually less than the diploid number of chromosome pairs, indicating the attraction between centromeres not only of homologous, but also of heterologous, chromosomes. By scanning microdensitometry, we have observed a constant ratio of chromocenter area: total nuclear area in giant cells. This ratio, which likely reflects the ratio of chromocenter volume: total nuclear volume, is in good agreement with that of satellite DNA: total DNA.
TL;DR: The G-band patterns of some of the chromosomes of these three species show striking similarities, suggesting identity, and auto-radiographic studies reveal that these centromeric regions replicate their DNA late in the S phase.
Abstract: In contrast to findings in many other species, the centromeric heterochromatin in cattle, goats, and sheep is unstained when the C-band method of Arrighi and Hsu (1971) is used. However, a modified C-band technique stains the centromeric heterochromatin strongly. This material also stains strongly with an acridine-orange reverse-banding method. The G-band patterns of some of the chromosomes of these three species show striking similarities, suggesting identity. Even some parts of the metacentric chromosomes of sheep, presumably resulting from Robertsonian fusions, can be identified as nearly unchanged chromosomes of the goat or of cattle. Auto-radiographic studies reveal that these centromeric regions replicate their DNA late in the S phase. Both 3H-thymidine and 3H-deoxycytidine are incorporated at these centromeric regions.
TL;DR: The distribution of heterochromatic regions in the chromosomes of diploid, tetraploid and hexaploid wheat showed that the B genome possesses characteristic large blocks as discussed by the authors.
Abstract: The distribution of heterochromatic regions in the chromosomes of diploid, tetraploid and hexaploid wheat shows that the B genome possesses characteristic large blocks. Though analyses of probable B genome donors indicate that Aegilops speltoides has a pattern of distribution of heterochromatin nearest to the B genome chromosomes, a polyphyletic origin of tetraploid wheat seems more plausible.
TL;DR: Using two differential Giemsa staining techniques, different staining patterns in the chromosomes of two higher plants, Allium cepa and Ornithogalum virens are found and suggest the basic similarity of higher plant and animal chromosomes.
Abstract: After the use of different Giemsa staining techniques, variations in chromosome banding patterns have often been observed in animal chromosomes. Such staining differences are usually interpreted to indicate that there is more than one type of heterochromatin in many animal chromosomes. Using two differential Giemsa staining techniques we have found different staining patterns in the chromosomes of two higher plants, Allium cepa and Ornithogalum virens . Furthermore, pericentric heterochromatin that occurs so commonly in animal chromo-somes was specifically Giemsa stained in O. virens . These results suggest the basic similarity of higher plant and animal chromosomes.
TL;DR: Non-replication of the alpha heterochromatin provides the explanation for the lowered amount of heterochromaatin in the polytene nuclei compared to their diploid counterparts.
Abstract: Replication in the chromocentre heterochromatin of salivary gland polytene nuclei of Drosophila melanogaster has been examined by 3H-thymidine EM autoradiography. In vitro pulse labelling of salivary glands from late third instar larvae showed that the chromocentre heterochromatin replicates in synchrony with the euchromatin in the nucleus. Within the chromocentre region, the central compact mass, identified earlier as the alpha heterochromatin, did not incorporate 3H-thymidine at any stage of the S, while the surrounding beta heterochromatin was always labelled in nuclei with labelled euchromatin. In a second set of experiments, growing larvae from just after hatching till late third instar stages, were fed on food containing 3H-thymidine, and at the end of larval life, the incorporation in salivary gland nuclei was examined by EM autoradiography. A grain density analysis of the EM autoradiographs revealed that the alpha heterochromatin does not replicate at all from after hatching till late third instar while the beta heterochromatin replicates as much as the euchromatin. Non-replication of the alpha heterochromatin provides the explanation for the lowered amount of heterochromatin in the polytene nuclei compared to their diploid counterparts. Implications of these observations on the organization of chromocentre heterochromatin in polytene nuclei and its homology to the heterochromatic regions in mitotic chromosomes are discussed.
TL;DR: It was demonstrated that nuclear DNA is elevated (near tetraploid stemlines) in carcinoma cells, the DNA concentration is more highly variable, and that the elevated DNA amounts are largely attributable to elevated nuclear area values.
Abstract: Summary Feulgen-stained normal breast epithelium (4 cases) and breast carcinoma (8 cases) were analyzed by means of cytophotometric scanning measurements. Besides the DNA content, DNA concentration, and area of the cell nucleus, the number and absolute as well as relative amount of condensed chromatin was determined. In addition, the DNA concentration, area, and form of the condensed chromatin was evaluated. It was demonstrated that nuclear DNA is elevated (near tetraploid stemlines) in carcinoma cells, the DNA concentration is more highly variable, and that the elevated DNA amounts are largely attributable to elevated nuclear area values. The number of “heterochromatic” particles is more variable in tumor cell nuclei than in normal cell nuclei. Significantly more chromocenters were demonstrable in only one case. The absolute DNA content in condensed chromatin of carcinoma cells is also highly variable (significantly elevated only in a single case). The most important result of the foregoing investigation seems to be that the percentage DNA content in condensed chromatin is greatly decreased in all tumors (6%) as compared to normal cell nuclei (13%). Regarding the form of the condensed chromatin particles, the particles ares more spherical in tumor cells as contrasted to more pointed in normal cells. The results are discussed in relationship to biochemical determinations of heterochromatin.
TL;DR: Observations and measurements of the amount and distribution of heterochromatin in interphase nuclei of the diploid and tetraploid species give further support to the conclusion that N. tomentosiformis rather than N. tabacum is the most likely progenitor of N. sylvestris and N. otophora.
Abstract: There are significant differences in nuclear DNA amount between both diploid and amphidiploid species of Nicotiana. Owing to the higher DNA density in the interphase nuclei of the amphidiploids DNA amounts tend to be underestimated by microdensitometry. After applying necessary corrections to amphidiploid readings it was found that: (1) The nuclear DNA amount in the tetraploid N. rustica is not significantly different from the sum of nuclear DNA amounts in reputed diploid parents, N. undulata and N. paniculata. (2) It is well established that N. sylvestris is one of the diploid progenitors of N. tabacum. The sum of the nuclear DNA amounts in N. sylvestris and N. tomentosiformis is not significantly different from that of the amphidiploid N. tabacum. In contrast the sum of the DNA amounts in N. sylvestris and N. otophora is significantly higher than that in N. tabacum. Observations and measurements of the amount and distribution of heterochromatin in interphase nuclei of the diploid and tetraploid species give further support to the conclusion that N. tomentosiformis rather than N. otophora is the second diploid progenitor of N. tabacum.
TL;DR: It was found that the duration of the total cell cycle and of each phase, but especially that of G1, was shorter in all the annuals studied, and a proposal is put forward to account for decreasing mitotic cycle time in spite of increased DNA amount.
TL;DR: An autosomal euchromatic maternal-effect mutant, abo (= abnormal oocyte), interacts with, or regulates the activity of, the heterochromatin of the sex chromosomes of Drosophila melanogaster, and it is shown that this interaction or regulation with the X chromosome involves a specificheterochromatic locus or small region that maps to the distal penultimate one-eighth of the basal X-chromosome heterochrome segment.
Abstract: An autosomal euchromatic maternal-effect mutant, abo (= abnormal oocyte), interacts with, or regulates the activity of, the heterochromatin of the sex chromosomes of Drosophila melanogaster. It is shown that this interaction or regulation with the X chromosome involves a specific heterochromatic locus or small region that maps to the distal penultimate one-eighth of the basal X-chromosome heterochromatic segment.
TL;DR: A working hypothesis is suggested according to which the X choromsome is inactivated during a critical stage of spermatogenesis in all male heterogametic organisms, as the inactivation is an essential control and not a compensatory step, leading to dominant male sterility.
Abstract: INACTIVATION of chromosomal elements is a process which takes place in various organisms, cell types, and cell cycle stages. The reasons for chromosome inactivation, which is superimposed on the more specific level of gene control, are different for the various systems. Dosage compensation in female mammals us. mitotic chromosome shut-off are the extreme cases. Since in many systems every chromosome may be in an active or inactive form, it is reasonable to assume, for the time being, that the molecular mechanism in different organisms is similar, thus justifying generalization. The role and behaviour of sex chromosomes during gametogenesis provide a striking example of differentiation of chromosomal elements and by inference reflect chromosome function. Precocious inactiviation of the X chromosome during seprmatogenesis together with activation of fertility factors on the Y in some organisms are of particular interest. In view of cytological and genetic observations we suggest a working hypothesis according to which the X choromsome is inactivated during a critical stage of spermatogenesis in all male heterogametic organisms. As the inactivation is an essential control and not a compensatory step, any interference with this process will change the developmental course of the spermatocyte leading to dominant male sterility (LIFSCHYTZ and LINDSEY 1972). In the course of this paper, the observations that support or lead to this view will be presented. Several experimental approaches we have undertaken to study further the genetics of the phenomenon, as well as its relation to Y chromsome activation, will be discussed.
TL;DR: The results suggest that the structure of APRT is defined by a locus on the long arm of human chromosome No. 16, which was consistently present in all of the clones and in one clone, it was the only human chromosome detected.
Abstract: Evidence for assigning the locus determining the structure of adenine phosphoribosyltransferase (APRT) to human chromosome No. 16 is presented. Hybrids of APRT-deficient mouse cells and of human fibroblasts having normal APRT were isolated by fusing the parental cells with Sendai virus, blocking de novo purine nucleotide synthesis with azaserine and selecting for hybrids that could use exogenous adenine. The hybrid clones that were studied had only APRT activity that was indistinguishable from human APRT with regard to electrophoretic migration and reaction with antibodies against the partially purified human enzyme. No. 16 was the only human chromosome consistently present in all of the clones, and in one clone, it was the only human chromosome detected. Selection against hybrid cells with 2,6-diaminopurine (DAP) yielded DAP-resistant survivors that lacked chromosome No. 16. One hybrid that originally had an intact No. 16 yielded adenine-utilizing subclones that lacked No. 16 but had a new submetacentric chromosome. The distribution of centromere-associated heterochromatin and the fluorescence pattern indicated that this chromosome consisted of a mouse telocentric chromosome and the long arm of No. 16. Cells having the submetacentric chromosome had human APRT. Both the enzyme and the chromosome were absent in DAP-resistant derivatives. These results suggest that the structure of APRT is defined by a locus on the long arm of human chromosome No. 16.