Showing papers on "Heterochromatin published in 1972"
TL;DR: A simple and direct fluorescence staining procedure is described by which chromosomal segments of constitutive heterochromatin and (in the mouse) sites of repetitious DNA can be visualized in mammalian chromosomes with a benzimidazol derivative “33258 Hoechst” belonging to a class of DNA-binding fluorochromes different from compounds of the Q-series.
324 citations
TL;DR: Unlike the case of mouse, human heterochromatin is composed of a variety of DNA families, and mapping human chromosomes by nucleic-acid hybridization appears feasible, the results suggest that repeated sequences in the DNA of the human genome suggest the heterogeneity of the repeated sequences.
122 citations
TL;DR: The distribution of sites capable of binding mouse satellite-complementary RNA in the cytological hybridization reaction has been examined in mouse liver and testis interphase nuclei to obtain a clear picture of the relationship of satellite DNA-containing structures to the rest of the interphase nucleus.
Abstract: The distribution of sites capable of binding mouse satellite-complementary RNA in the cytological hybridization reaction has been examined in mouse liver and testis interphase nuclei. The approach taken has been to combine hybridization with semi-thin sectioning and autoradiography in order to obtain a clear picture of the relationship of satellite DNA-containing structures to the rest of the interphase nucleus. In liver nuclei, hybridization occurs primarily with blocks of heterochromatin associated with the nuclear envelope. The most prominent of these, in terms both of size and intensity of hybridization, is the nucleolar stalk and the rest of the nucleolus-associated heterochromatin. The nucleolar body itself is not labeled, nor is much of the peripheral condensed chromatin ; in fact, a polarized distribution of satellite DNA is evident. In Sertoli and spematid nuclei, satellite DNA is found in a small number of large heterochromatin blocks with which the nucleolus is associated; some of this material bears a relationship to the nuclear envelope in these cells also.
102 citations
TL;DR: The buoyant density, satellite composition, and in some cases renaturation kinetics of the DNA of whole nuclei, euchromatin, heterochromatin + nucleoli and pure nucleoli, were determined in the mouse, guinea pig, horse, dog, Chinese hamster, Microtus agrestis, chicken and Japanese quail.
76 citations
TL;DR: It was shown that the ribosomal cistrons (rDNA) are located in the nucleolus organizing system (satellite, nucleolar constriction and organizer) of the satellited chromosome pairs I (S1) and V (S2), in the proximal heterochromatic segment of the long arm of chromosomes S1 and in the terminal heterochrome segment of chromosome pair II.
Abstract: Tritiated ribosomal RNA (rRNA) was prepared from hypocotyls of Phaseolus coccineus grown in liquid culture in the dark and in presence of 5-3H-uridine. A mixture of the 18S and 25S 3H-rRNA fractions was used for hybridization with DNA in the polytene chromosome cells of the embryo suspensor of P. coccineus. It was shown that the ribosomal cistrons (rDNA) are located in the nucleolus organizing system (satellite, nucleolar constriction and organizer) of the satellited chromosome pairs I (S1) and V (S2), in the proximal heterochromatic segment of the long arm of chromosomes S1 and in the terminal heterochromatic segment of chromosome pair II. The micronucleoli which are produced by the satellite and nucleolus organizer of the chromosome pair S1 contain rDNA; on the contrary, no rRNA-DNA hybridization is found in the DNA containing granules which are produced by the satellite and nucleolus organizer of chromosome pair S2. The DNA which is amplified during production of DNA puffs at some chromosomal regions apparently does not code for ribosomal RNA (no detectable rRNA-DNA hybridization).
53 citations
TL;DR: When isolated nuclei of the male mealy bug are incubated with tritiated acetyl coenzyme A, label is incorporated into 70–75% of the nuclei, suggesting that the incorporation largely represents enzymatic, post-synthetic acetylation of histone.
47 citations
TL;DR: The satellite DNAs of D. ordii are non-randomly distributed within the chromosome and are responsible for the pattern of heterochromatin of metaphase chromosomes, which concludes that the shorter arms of chromosomes are largely if not entirely composed of satellite DNA.
45 citations
TL;DR: The frequent appearance of subcomponents in the curves of pulse-labeled DNA centrifuged in cesium chloride suggest there are families of DNA sequences of similar base composition that tend to replicate at similar times, and suggest that the shift in base composition of DNA replicated during the latter part of the S period is a reflection of the distinct types of DNA present in heterochromatin.
44 citations
TL;DR: A comparison of the density patterns of partially re-associated DNA from animals of different genetic constitution reveals that a large proportion of this highly repetitive DNA is located in the heterochromatic arm of the X chromosome, and that more than 60% of the DNA in this chromosome region is highly repetitive.
42 citations
TL;DR: It was found that in all 3 mosaic cultures the 45,X cells had a faster cell cycle than the second cell population and it is argued that heterochromatin has a retardative effect on cell division.
Abstract: Fibroblasts were grown from skin explants of 3 human females who are sex chromosome mosaics. The 3 cultures had the following chromosome complements: 45,X/46,XX, 45,X/46,XXqi and 45,X/47,XXX. Using thymidine labelling and Colcemid accumulation of metaphases it was found that in all 3 mosaic cultures the 45,X cells had a faster cell cycle than the second cell population. The difference in cell cycle duration was attributed to the longer G1 phase in the cells with 2 or 3 X chromosomes. The 2 populations of cells in the mosaic only differ in the number of heterochromatic X chromosomes and it is argued that heterochromatin has a retardative effect on cell division.
38 citations
TL;DR: When human genome was fractionated by thermal elution chromatography, repetitious DNA was found in every arbitrary temperature segment, and when these repetitiousDNA families were used for in situ hybridization, the following conclusions were evident.
Abstract: When human genome was fractionated by thermal elution chromatography, repetitious DNA was found in every arbitrary temperature segment. When these repetitious DNA families were used for in situ hybridization, the following conclusions were evident: (a) Unlike the case of mouse, where essentially all centromeric heterochromatins appear to be composed of one DNA family, human heterochromatin is composed of various DNA families. (b) Some human heterochromatin pieces, (e.g., that of chromosome 9) appear to have more heterogeneous composition than others (e.g., that of chromosome 1). (c) The highly repetitious human DNA fractions are located primarily at the centromeric and telomeric regions, but the interstitial regions also contain these fractions. (d) The more slowly reassociating repetitious sequences are distributed over the length of the chromatid, with a slight bias in favor of the telomeric regions. (e) The repetitious DNA fractions of higher (guanine + cytosine) content have less affinity for the centromeric regions.
TL;DR: In this paper, the occurrence of the various highly repetitive DNA fractions in Drosophila hydei DNA identified by hybridization across gradients was studied in tissues of different levels of polyteny (fat body, about 128 C; salivary glands, about 1024 C).
TL;DR: The interesting phenomenon of the ability of the mouse centromeric heterochromatin to bind QM in interphase though not in metaphase is reported.
TL;DR: The number of nucleoli and the relations between them and chromosomes in the human fetal oöcyte have been investigated and the opinion that there are multiple sites for the synthesis of the various nucleolar componnents is supported.
Abstract: The number of nucleoli and the relations between them and chromosomes in the human fetal oocyte have been investigated in this study. The differences existing between first oocytes and spermatocytes have been emphasized. These differences concern essentially the number of nucleoli, the stage during which they appear and the quantity of heterochromatin associated with the nucleoli. The latter appear very early in the oocyte: they are already present at the beginning of the preleptotene stage. This stage is characterized by the processes of spiralization and despiralization, heretofore not described. The first prophase is characterized by the presence of abundant nucleolar material, especially in the diplotene stage. This abundance is certainly in relation with the active protein synthesis which characterizes the growth of the oocyte. As in the spermatocyte of the pachytene stage, the majority of nucleolar chromosomes, in the oocyte, are acrocentric. But in the latter, the quantity of heterochromatin associated with the nucleolus greatly exceeds the quantity present in the nucleolar organizers of acrocentric chromosomes, particularly during the leptotene stage. This supports the opinion that there are multiple sites for the synthesis of the various nucleolar componnents. Also discussed are the roles of heterochromatin and nucleolar organizers in nucleogenesis.
TL;DR: The distribution of repetitive DNA in the chromosomes of Microtus agrestis was studied with the method for demonstrating constitutive heterochromatin given by Yunis et al. (1971) and the reassociation technique described by Schnedl (1971).
Abstract: The distribution of repetitive DNA in the chromosomes of Microtus agrestis was studied with the method for demonstrating constitutive heterochromatin given by Yunis et al. (1971) and the reassociation technique described by Schnedl (1971). All autosomes can be individually recognized by means of the position of their bands. The euchromatic segment of the X1 chromosome shows the same banding pattern as the corresponding segment of X2 which consists of facultative heterochromatin. The short arms of the Y chromosome are not deeply stained with either method and therefore do not contain noticeable amounts of repetitive DNA. The relative distances between the bands remain constant during chromosome contraction in mitosis.
TL;DR: In situ hybridisation of radioactive complementary RNA has been used to localise the G-C rich repetitious DNA satellite in chromosomes of the Japanese quail.
Abstract: In situ hybridisation of radioactive complementary RNA has been used to localise the G-C rich repetitious DNA satellite in chromosomes of the Japanese quail. The satellite sequences are located predominantly in the microchromosomes. No cross hybridisation is found with duck or chicken microchromosomes. The relationship between repetitious DNA, heterochromatin and nucleolus-organisation is discussed.
TL;DR: Satellites and other repeated polynucleotide sequences are under-represented in the polytene, salivary gland cells of Drosophila melanogaster, D. virilis and D. hydei larvae but are fully represented in diploid cells from embryos and imaginal disks.
Abstract: SATELLITE DNAs are heavily concentrated in the centromeric heterochromatin of metaphase chromosomes1–3. Satellites and other repeated polynucleotide sequences are under-represented in the polytene, salivary gland cells of Drosophila melanogaster, D. virilis and D. hydei larvae but are fully represented in diploid cells from embryos and imaginal disks4–6. This under-representation in polytene cells stems from the association of heterochromatin in the chromocentre and the progressive under-replication of the chromocentre during larval development7,8.
TL;DR: The Algerian hedgehog (Aethechinus ) has a diploid chromosome number of 48, similar to the European hedgehog species and to the long-eared Asiatic hedg.
Abstract: The Algerian hedgehog (Aethechinus ) has a diploid chromosome number of 48, similar to the European hedgehog species (Erinaceus ) and to the long-eared Asiatic hedg
TL;DR: It is suggested that extra heterochromatin from either the X or Y chromosome in either the mother or her progeny can reduce the mortality caused by da in development and can also reduce the abnormality in oogenesis, although this is obscured by the severity of the maternal effect.
Abstract: The genetic properties of a recessive autosomal point mutant, "daughterless" (symbol: da ), are described. They are: (1) da maps in the euchromatin of 2L at about position 39 on the genetic map and between 27D and 31E on the salivary map; (2) when homozygous in females, da causes the production of unisexual male progenies owing to sex differential zygote mortality in the egg stage; (3) da has no effect on the progeny of mutant males; (4) female zygotes die, while at least some male zygotes survive, irrespective of the number of Y chromosomes or the amount of X -chromosome heterochromatin carried by either the mutant female or her progeny; (5) homozygous da progeny of heterozygous parents also show sex differential survival favoring males indicating a da effect in development as well as in oogenesis, but with the developmental effect much less pronounced; (6) extra heterochromatin from either the X or Y chromosome in either the mother or her progeny can reduce the mortality caused by da in development (and, therefore, conceivably can also reduce the abnormality in oogenesis, although this is obscured by the seventy of the maternal effect.)——From these results, it is suggested that (1) da regulates either the activity of structural genes in the sex chromosome heterochromatin or the activity or stability of their products, and (2) it is a defective product of sex chromosome heterochromatic genes that causes the abnormalities resulting in the observed mortality of heterozygous progeny of homozygous mutant m3thers and of homozygous mutant progeny of heterozygous mothers.——The striking parallels with the properties of the gene, "abnormal oocyte" are noted as is the close linkage between the two loci. The possibility of a special sex-chromosome-heterochromatin-regulator region on chromosome 2 is considered.
TL;DR: Hydlysis kinetics in both euchromatin and heterochromatin are identical and it is suggested that “atypeness” of hydrolysis curves are not due to different hydrolytic properties of diffuse and condensed chromatin.
Abstract: Feulgen hydrolysis kinetics were investigated in euchromatin and heterochromatin separately using forebrain ganglionar cells of the field vole, Microtus agrestis L. In females of this species two large heterochromatic blocs are formed by the huge X-chromosomes containing 20% of the cell's DNA content and occupying 5.5% of the nuclear surface. The cells were stained according to the Feulgen procedure following different hydrolysis times. Absorbance data were extracted from the microscopic images by the scanning microphotometer UMSP I, punched into paper tape and fed to an IBM 1130 computer. Data were processed for the separation of grid points belonging to heterochromatin and euchromatin, respectively. “Heterochromatin points” were defined to be the points with the highest absorbance and forming 5.5% of the nuclear surface area, the rest being euchromatin. For each chromatin fraction the total dye content was calculated. The proportion of dye amount in the heterochromatin part was found to be 20% of the total cell nucleus and is independent of hydrolysis time. Hydrolysis kinetics in both euchromatin and heterochromatin are identical. It is suggested that “atypeness” of hydrolysis curves are not due to different hydrolysis properties of diffuse and condensed chromatin. Von Feulgengefarbten Ganglienzellkernen der Erdmaus,Microtus agrestis L., wurden die cytophotometrisch gemessenen DNA-Werte auf Lochstreifen gestanzt. Die beiden Kernbezirke, der dem Eu- und der dem Heterochromatin angehorende, wurden durch bildanalytische Auswertung (picture processing) des mikroskopischen Kernbildes mit einer Datenverarbeitungsanlage getrennt. Es konnten keine Unterschiede im Verlauf der Hydrolysekinetik gefunden werden.
TL;DR: It is shown that the late replicating segments are stained by the C-banding technique and a method for exclusively demonstrating centromeric heterochromatin is described, which shows good agreement between the multiple banding pattern produced by fluorescent and Giemsa stain.
Abstract: In the Romanian hamster (2n=38) a number of whole chromosome arms is heterochromatic. This offers the opportunity to test the effect of some recently developed differential staining techniques upon heterochromatin. It is shown that the late replicating segments are stained by the C-banding technique. A method for exclusively demonstrating centromeric heterochromatin is described. With this, only 8 autosome pairs and the X-chromosome show centric heterochromatin. There is a good agreement between the multiple banding pattern produced by fluorescent and Giemsa stain.
TL;DR: Nuclear subfractionation studies show that heavy shoulder DNA is markedly increased in the heterochromatin fraction of Japanese quail nuclei, but not in the chicken.
TL;DR: 2 male patients with G-trisomic Down's syndrome, were studied for constitutive heterochromatin pattern by the technique of Arrighi and Hsu (1971) and 2 G-chromosomes were found to have heterochROMatin distributed around the centromeric areas.
Abstract: 2 male patients with G-trisomic Down's syndrome, were studied for constitutive heterochromatin pattern by the technique of Arrighi and Hsu (1971). 2 G-chromosomes were found to have heterochromatin distributed around the centromeric areas and the remaining 3 were free of such localized heterochromatin blocks; the extra G-chromosome belonging to the non-localized heterochromatin members.
TL;DR: It is considered possible that the preferential attack on the pericentromeric heterochromatin previously observed in chromosome breakage studies with dehydroheliotridine may be due to its effects on the synthesis of satellite DNA.
TL;DR: The finding of accelerated DNA synthesis in autosomal heterochromatin lends itself to several possible explanations, although it remains difficult to understand fully at present.
Abstract: The time sequence of DNA synthesis of autosomal constitutive heterochromatin and euchromatin was studied in kidney-cell cultures of the European hedgehog which had been pulse labeled with 3H-thymidine. The mean length of the S-period is 10.4 h for euchromatin and 5.2 h for constitutive heterochromatin. Thus the latter replicates DNA twice as fast as euchromatin. Constitutive heterochromatin starts replicating DNA about 7 h later and finishes 1.5 h later than euchromatin. The asynchrony of DNA synthesis between the two types of chromatin is particularly marked in the beginning of the S-phase. The inactive X chromosome also synthesizes DNA faster than euchromatin; it begins a short time before and finishes slightly after constitutive heterochromatin. The finding of accelerated DNA synthesis in autosomal heterochromatin lends itself to several possible explanations, although it remains difficult to understand fully at present.
TL;DR: The “open” structure of nucleohistones finds a plausible explanation in the fact that amino acid sequence analysis of several histones revealed an asymmetric distribution of charged groups and that therefore only these protein fractions can interact with DNA.
Abstract: The progress made in molecular biology has provided definite evidence that DNA is the genetic material of all cellular organisms. It is mainly localized within the cell nuclei and, in association with histones and acidic proteins, forms the fundamental structure of the chromosomes. The DNA-protein complex, called nucleohistone or chromatin, represents the sum of all existing genes of one cell type and can be considered as a functional genetic unit. All genetic structures contain this fundamental element and only their steric arrangement or multiplicity determine the species-specific differences in chromosomal morphology. The preservation of the three-dimensional structure seems to be the function of histones which, in general, are associated with densely packed and metabolically inactive DNA sequences. The lysine-rich histone I probably has a specific regulatory function since it inhibits the transcription of certain genes. Acidic proteins are mainly to be found in stretched chromosomal structures of high metabolic activity which accentuate the correlation between structure and function of nucleohistones. Approximately 50% of the DNA of the nucleohistone complex is not masked by proteins though only a small percentage of the free nucleotide sequences can be transcribed by RNA polymerase. The “open” structure of nucleohistones finds a plausible explanation in the fact that amino acid sequence analysis of several histones revealed an asymmetric distribution of charged groups and that therefore only these protein fractions can interact with DNA. In Crick's recently published model of the chromosomal organization the unique structure of histones is taken into account and it is assumed that the histone-rich heterochromatin contains multiple but untranscribable control elements. Functional genes are represented by a single stranded DNA duplex within the interbands which utilize a special protein to preserve this unique conformation.
TL;DR: In this article, the authors investigated the Zellstruktur von Leberzellen der Erdmaus, Microtus agrestis, wurde nach Giemsafarbung, Feulgen-behandlung, Behandling with Ribonuklease and nach Farbung des konstitutiven Heterochromatins untersucht.
Abstract: Die Zellstruktur von Leberzellen der Erdmaus, Microtus agrestis, wurde nach Giemsafarbung, Feulgenbehandlung, Behandlung mit Ribonuklease und nach Farbung des konstitutiven Heterochromatins untersucht. Das konstitutive Heterochromatin ist in Leberzellen nicht heteropyknotisch, das fakultative Heterochromatin ist im weiblichen Geschlecht als Sexchromatinkorperchen sichtbar. Bestimmungen des relativen DNS-Gehalts ergaben, das die Zahl der Sexchromatinkorperchen der Ploidie der Zellkerne proportional ist. Die Nukleolen liegen in Hepatozyten oft randstandig; in 59% der diploiden Zellkerne sind 2 Nukleolen enthalten. Nach Anfarbung der repetitiven DNS werden oft auch die Nukleolen gefarbt, nach Ribonukleasebehandlung tritt dieser Effekt nicht auf. Das konstitutive Heterochromatin wird in Form von 2 langen fadigen Strukturen sichtbar.