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Showing papers on "Nuclear DNA published in 1973"


Journal ArticleDOI
TL;DR: Mitochondrial DNA was found to be significantly less methylated than nuclear DNA with respect to 5-methylcytosine in all cell types studied and by all methods used.

136 citations


Journal ArticleDOI
TL;DR: DNA isolated from macronuclei of the ciliate, Tetrahymena pyriformis, has been found to contain [6N]methyl adenine (MeAde); this represents the first clear demonstration of significant amounts of MeAde in the DNA of a eucaryote.
Abstract: DNA isolated from macronuclei of the ciliate, Tetrahymena pyriformis, has been found to contain [6N]methyl adenine (MeAde); this represents the first clear demonstration of significant amounts of MeAde in the DNA of a eucaryote. The amounts of macronuclear MeAde differed slightly between different strains of Tetrahymena, with approximately 0.65–0.80% of the adenine bases being methylated. The MeAde content of macronuclear DNA did not seem to vary in different physiological states. The level of MeAde in DNA isolated from micronuclei, on the other hand, was quite low (at least tenfold lower than in macronuclear DNA).

129 citations


Journal ArticleDOI
TL;DR: The capacity of unlabeled cell DNA to accelerate the reassociation of labeled double-stranded DNA synthesized by the Rous sarcoma virus RNA directed DNA polymerase is measured and is supported by evidence that the techniques employed detect the formation of extensive well-matched duplexes of cell DNA and viral polymerase products.

108 citations


Journal ArticleDOI
TL;DR: An improved method is described for making chromosome spreads of the plasmodium of the myxomycete, Physarum polycephalum, which consists of isolating metaphase nuclei, spreading the chromosomes with hot lactic acid, and staining with acetic-orcein.

81 citations


Journal ArticleDOI
TL;DR: The results emphasize the existence of extensive interspecific variations in the amounts of DNA in the Amphibia, as well as certain facts of possible systematic interest: the Urodela possess greater amounts of nuclear DNA than most of the Apoda and the Anura.
Abstract: SUMMARYUsing blood smears, stained with Feulgen's reaction, a study has been made of the nuclear DNA content of an Apode, thirteen species of Urodela and twenty-three species of Anura, certain of which belong to old and important families on account of the complex phylogeny of these Amphibia.The results of this study emphasize the existence of extensive interspecific variations in the amounts of DNA in the Amphibia, as well as certain facts of possible systematic interest: the Urodela possess greater amounts of nuclear DNA than most of the Apoda and the Anura; however, some of the more primitive species existing today (genus Hynobius) have DNA amounts that are relatively low in the order; in the Amphibia, the variations in the DNA amounts do not seem to be correlated with the behaviour of the phylogeny but seem rather to reflect phenomena of redundancy.The theories that have been put forward so far on the significance of the quantitative variations in the DNA of the Amphibia seem to be at least partly con...

78 citations


Journal ArticleDOI
TL;DR: The findings are consistent with and would appear to be best explained by the theory of the symbiotic origin of the plastids, as a close positive correlation exists between the number of plastid in a cell and the amount of DNA in the nucleus.
Abstract: For a given cell type and genotype a close positive correlation exists between the number of plastids in a cell and the amount of DNA in the nucleus. Comprehensive evidence is presented. The duplication of the DNA amount entails an increase of the plastid number in differentiating cells by about 70%. Exceptions reported in the literature are critically examined. The odds are in favour of the assumption that exceptions to the rule which are not due to special circumstances do not exist. In meristematic cells even a duplication of the plastid number will occur, for cells without plastids are not to be found. The plastids are always ready to divide, the interpretation goes, but the size of their populations is limited by the amount of nuclear DNA. Thus meristematic cells manage to control their plastid populations by releasing once in a cell cycle the brakes imposed upon plastid division, whereupon the plastids make use of their newly won freedom, dividing until the old ratio between plastid number and nuclear DNA amount is established again. As a shorter time is needed for plastid division than for mitosis, there is no danger of cells arising without plastids; no distributing mechanism is required if at least three to four plastids are present in a cell. The findings are consistent with and would appear to be best explained by the theory of the symbiotic origin of the plastids.

70 citations


Journal ArticleDOI
TL;DR: Sheared, denatured cytoplasmic membrane-associated DNA reassociates as two distinct fractions whose rates of reassociation differ by about four decades: the complexity of the reassociation of this DNA tends to rule out the possibility that it arises from either mycoplasmal or viral contamination of cell cultures.

65 citations


Journal ArticleDOI
TL;DR: Electron microscopic analysis indicates that yeast nuclear DNA can be isolated as linear molecules ranging in size from 50 mum (1.2 x 10(8) daltons) to 355 mum (8.4 x 10 (8)Daltons), consistent with the hypothesis that each yeast chromosome contains a single, linear DNA duplex.
Abstract: Electron microscopic analysis indicates that yeast nuclear DNA can be isolated as linear molecules ranging in size from 50 μm (1.2 × 108 daltons) to 355 μm (8.4 × 108 daltons). Analysis indicates the data is consistent with the hypothesis that each yeast chromosome contains a single, linear DNA duplex. Mitochondrial DNA molecules have a contour length of 21 ± 2 μm and are mostly linear.

61 citations


Journal ArticleDOI
TL;DR: The results reflect the close relationship between the nuclear envelope and (constitutive) heterochromatin, but also indicate that membrane binding is not restricted to this material.

60 citations


Journal ArticleDOI
10 Oct 1973-Nature
TL;DR: The generality of the organization of transcribing rDNA, another amplified rDNA system, is examined, in order to examine the extrachromosomal DNA masses which occur in the oocytes of diverse insects and constitute a considerable amount of the total nuclear DNA.
Abstract: The DNA molecules which contain the cistrons for ribosomal RNA (rDNA) consist of repeats of alternating segments of (i) regions which are transcribed into the primary rRNA precursors (pre-rRNA) and (ii) regions which are either not transcribed (corresponding to “spacers” sensu Miller and Beatty1) or might be, perhaps in parts, transcribed into RNA molecules which, however, are not covalently. linked with pre-rRNA (“spacers” sensu Reeder and Brown2 ; for demonstration of partial transcripts from spacers see Scheer et al.3). The relative arrangement of the “spacer” units and the stretches coding for pre-rRNA (corresponding to the matrix units of Miller and Beatty1,4) has been elucidated by different methods in chromosomal and extrachromosomal rDNA of diverse amphibian species, including urodeles and anurans1,3–13. In the clawed toads, Xenopus laevis and X. muelleri, according to differential DNA denaturation studies12,13, this pattern of arrangement is identical in both chromosomal (“nucleolus organizer”) and extrachromosomal (“amplified”) rDNA. Extrachromosomal nucleolar material consisting of the actively transcribing amplified rDNA is especially suitable for biochemical and electron microscopic studies because it provides a natural enrichment of this kind of DNA in a state which is topologically isolated from all the other chromatin. We have therefore chosen, in order to examine the generality of the organization of transcribing rDNA, another amplified rDNA system, the extrachromosomal DNA masses which occur in the oocytes of diverse insects and constitute a considerable amount of the total nuclear DNA (for example, 59% in Tipula oleracea14, 23–35% in Dytiscid beetles15 and 14–31% in Acheta domesticus 16–19 ). As has been shown by numerous authors18,20–24 a favourable material in this respect is the house cricket, A. domesticus.

60 citations


Journal ArticleDOI
TL;DR: The data suggest that evolution by polyploidy may be more common in crustaceans than earlier data had indicated and recommend the Crustacea for further studies in evolutionary genetics.
Abstract: Nuclear DNA amounts have been determined for 42 species of crustaceans bringing the total number of species with known nuclear DNA content to over 70. Genome size in Crustacea varies over a 25-fold range with a modal value of 2 to 3 pg haploid being common in many groups. Both average genome size and the amount of variability among species are characteristic for certain groups. A trend towards small genomes is evident in advanced and specialized crustacean groups. Somatic polyploidy is a very pronounced feature of the Crustacea. The data suggest that evolution by polyploidy may be more common in crustaceans than earlier data had indicated. These features and the presence of very characteristic satellite fractions in the nuclear DNA recommend the Crustacea for further studies in evolutionary genetics.

Journal ArticleDOI
TL;DR: Cell autoradiography of cultures labelled in various regimes showed that at this time there is a cyclo heximide-transition point at which the cell acquires the capacity to both initiate and complete a whole round of replication in the presence of 100 μg/ml of cycloheximide.

Journal ArticleDOI
TL;DR: Results indicate that the DNA increase involves replication of the whole genome (endoreduplication) during the cell expansion phase of cotyledon development.
Abstract: In Vicia faba L., the tissue specific proteins, legumin and vicilin, are synthesized during the cell expansion phase of cotyledon development. During this growth period, RNA and nuclear DNA increase 8- to 10-fold. 3H-Uridine and 3H-adenosine are incorporated into ribosomal RNA, both 25S and 18S, and into transfer RNA. DNA isolated from cotyledons in the cell division phase of growth has been compared with DNA isolated from cotyledons undergoing expansion growth. Results indicate that the DNA increase involves replication of the whole genome (endoreduplication).

Journal ArticleDOI
TL;DR: The kinetic data combined with the behavior of the high specific activity chromatin fraction indicate that the heparin effect on endogenous DNA synthesis may have more than one component.

Journal ArticleDOI
TL;DR: In situ hybridization techniques indicate that component α sequences aggregate in clumps inuclei of growing cells and show a diffuse distribution in nuclei of confluent cells, which suggests that centromeric regions of the various chromosomes or groups of chromosomes aggregate and disaggregate reversibly as the culture changes from density-dependent growth inhibition to active cell division.
Abstract: About 20 to 25 percent of the nuclear DNA from cultured cells of the African green monkey, Cercopithecus aethiops, consists of a homogeneous, highly repetitive fraction designated C. aethiops component α DNA. Use of in situ hybridization techniques reveals component α at the centromeres of chromosomes from both diploid and heteroploid African green monkey kidney (AGMK) tissue culture cells. — Component α DNA comprises 47 percent of the nucleolar DNA in actively growing primary AGMK cells, but only 31 percent of the nucleolar DNA in confluent cells which show density-dependent growth inhibition. Further, there is a pronounced shift of both main band and component αDNA from euchromatin to heterochromatin when growing cells attain confluency. Thus, the relative subnuclear distributions of component α and main band DNA's are different in growing and confluent cells. — In situ hybridization techniques indicate that component α sequences aggregate in clumps in nuclei of growing cells and show a diffuse distribution in nuclei of confluent cells. This suggests that centromeric regions of the various chromosomes or groups of chromosomes aggregate and disaggregate reversibly as the culture changes from density-dependent growth inhibition to active cell division. — Hypotonic citrate treatment of primary AGMK cells causes nucleoli of confluent cells to disperse: this dispersion following citrate treatment was not seen in growing AGMK cells or in confluent or growing heteroploid cells. Similarly, this nucleolar dispersion was seen in confluent diploid mouse and human cells but not in growing diploid cells or in confluent or growing heteroploid cells.

Journal ArticleDOI
TL;DR: No evidence was found for a level of DNA synthesis commensurate with that expected from the cytophotometric data after the administration of tritiated thymidine during the age period representative for the increase in Feulgen DNA.

Journal ArticleDOI
10 Oct 1973-Nature
TL;DR: Large differences exist within a single genus between species with the same diploid chromosome number, for example, a three-fold range in the genus Lathyrus4 and between five and seven times as much nuclear DNA in Vicia faba as in V. sativa.
Abstract: THERE is widespread variation between species of higher plants in amounts of nuclear DNA. In ten species a fifty-seven-fold variation in amounts of DNA per nucleus for equivalent cells was recorded1 and later reports showed wide ranges in the DNA contents of diploid species within single families (forty-fold in the Ranunculaceae2 and sixty to eighty-fold in the Droseraceae3). Most strikingly, large differences exist within a single genus between species with the same diploid chromosome number, for example, a three-fold range in the genus Lathyrus4 and between five and seven times as much nuclear DNA in Vicia faba as in V. sativa5–7. The structural basis of these variations is unclear although models of either a single stranded chromosome, in which DNA content increases by longitudinal multiplication of DNA sequences, or a multi-stranded chromosome, where increase is by lateral increase of strands, have been suggested (see reviews, refs 8, 9).

Journal ArticleDOI
22 Aug 1973-Nature
TL;DR: A large number of experiments have shown that the nucleus of the L genotroph contains 16% more DNA than that of S, with PI intermediate, and this change in nuclear DNA content appears to be essential for successful induction.
Abstract: HERITABLE changes in plant weight are induced in flax by specific growth environments. Conditioning of the original plastic genotroph (PI) produces a large stable form (L) or a small stable form (S), according to the fertilizers applied1,2. A large number of experiments have shown that the nucleus of the L genotroph contains 16% more DNA than that of S, with PI intermediate3–5. This change in nuclear DNA content, arising during the first 5 weeks of induction, appears to be essential for successful induction. The nature of the additional DNA present in the L genotroph, which presumably regulates the expression of the genotype, is therefore of great interest.

Journal ArticleDOI
TL;DR: It is shown that the leukemic member contains particle-related sequences in the DNA of his leukocyte that cannot be detected in the leukocytes of his healthy identical sibling, implying that the additional leukemia-specific information found in theDNA of the leukedmic individuals must have been inserted subsequent to fertilization.
Abstract: The discovery in human leukemic cells of particulate elements encapsulating 70S RNA and RNA-directed DNA polymerase made possible the synthesis of a [3H]DNA probe that could detect leukemia-specific sequences in the DNA of normal and leukemic individuals. In an earlier study of a series of unrelated leukemic patients, we established that the nuclear DNA of their leukemic cells contain particle-related sequences that cannot be detected in leukocytes of normal individuals. This result is inconsistent with the virogene concept that demands the inclusion of one complete copy of oncogenic information in the genome of every normal cell. The present study carries this analysis one step further by showing, with two sets of identical twins, that the leukemic member contains particle-related sequences in the DNA of his leukocytes that cannot be detected in the leukocytes of his healthy identical sibling. This finding implies that the additional leukemia-specific information found in the DNA of the leukemic individuals must have been inserted subsequent to fertilization. This outcome argues against the virogene hypothesis or any other etiologic concept that invokes vertical transmission through the germ line of the particle-related information found uniquely in the DNA of leukemic cells.

Journal ArticleDOI
TL;DR: MNNG was found to selectively mutate replicating forms of nuclear DNA in synchronized cultures of Chlamydomonas reinhardtii and mutagenesis at the time of chloroplast DNA replication resulted in a 1.6-fold increase in the recovery of both sr-1 and sr-2 induced mutants.
Abstract: In synchronized cultures of Chlamydomonas reinhardtii N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) was found to selectively mutate replicating forms of nuclear DNA. This conclusion was based on the 15- to 30-fold increase in the recovery of MNNG induced Mendelian streptomycin resistant mutants (sr-1) which was correlated with mutagenesis during the period of nuclear DNA replication. No concomitant increase in the recovery of non-Mendelian streptomycin resistant mutants (sr-2) occurred during this same period. Mutagenesis at the time of chloroplast DNA replication, however, resulted in a 1.5- to 1.6-fold increase in the recovery of both sr-1 and sr-2 induced mutants.

Journal ArticleDOI
TL;DR: Unscheduled incorporation of tritium-labeled thymidine into nuclear DNA, induced by UV irradiation and presumed to indicate DNA repair replication, has been followed in differentiating male germ cells of the rat and rabbit by quantitative autoradiographic techniques.
Abstract: Unscheduled incorporation of tritium-labeled thymidine into nuclear DNA, induced by UV irradiation and presumed to indicate DNA repair replication, has been followed in differentiating male germ cells of the rat and rabbit by quantitative autoradiographic techniques. Cells at various stages of differentiation incorporated [3H] thymidine at different rates. The maximal rate was observed in nuclei of pachytene primary spermatocytes; the rate was markedly lower in spermatogonia and in leptotene and zygotene primary spermatocyte nuclei. No evidence of incorporation was found for nuclei of spermatids and testis spermatozoa.

Journal ArticleDOI
15 Aug 1973-Nature
TL;DR: This approach was based on the observation that arginine deprivation of Rous sarcoma virus transformed rat cells induced the synthesis and release of C type virions, and suggested that the isolation and characterization of virus-like particles may be possible in conditions which induce the leukaemic cells to produce virions.
Abstract: STUDIES on human leukaemic cells reveal the presence in the cytoplasmic fraction of an RNase sensitive DNA polymerase1 complexed with 70S RNA2 and virus specific polysomal RNA3. The DNA product of this enzymatic reaction specifically hybridized to leukaemic nuclear DNA and not to nuclear DNA from normal leukocytes4. This does not establish a viral aetiology for human leukaemia, but suggests that such a possibility may exist. The isolation and characterization of virus-like particles may therefore be possible in conditions which induce the leukaemic cells to produce virions. Our approach was based on the observation5 that arginine deprivation of Rous sarcoma virus (RSV) transformed rat cells (which do not synthesize virions) induced the synthesis and release of C type virions. We have found that leukaemic cells, obtained from patients with acute lymphoblastic leukaemia (ALL) and chronic lymphoblastic leukaemia (CLL) and myeloblastic leukaemia, when incubated in an arginine deficient medium, released particles labelled with 3H-uridine which banded at a density of 1.17 g ml−1. These particles were found to contain an RNase sensitive DNA polymerase activity which transcribed DNA from 70S RNA molecules and formed 70S RNA : DNA hybrid molecules.

Journal ArticleDOI
TL;DR: Molecular properties of the monomer resembled nuclear DNA polymerase: sedimentation coefficient, template specificity and resistance to inhibition by N -ethylmaleimide and heparin.

Journal ArticleDOI
TL;DR: Isolated rat liver mitochondria are capable of incorporating labeled deoxynucleoside triphosphates into DNA, and the buoyant density of the denatured and reannealed labeled product is identical with that of similarly treated authentic mitochondrial DNA in contrast to nuclear DNA.

Journal ArticleDOI
TL;DR: It is shown that mitochondrial DNA synthesis continues at a normal rate in a cells for at least 6 hours in the presence of α factor, resulting in a 5-fold increase in the amount of mitochondrial DNA per cell.

Journal ArticleDOI
TL;DR: Continuing methylation of parental DNA has been shown, by density shift experiments and by the conversion of prelabeled DNA-cytosine to DNA-5-methylcytOSine, which once formed was found to be stable.

Journal ArticleDOI
TL;DR: Quantitative renaturation kinetic studies of purified kinetoplast minicircular DNA from Leishmania tarentolae indicated that there is probably one but certainly no more than two classes of identically sized minicircles in terms of DNA base sequences.

Journal ArticleDOI
TL;DR: The incorporation of 3H‐TTP into the nuclei, like the cell free DNA polymerase assay, is largely dependent on the presence of all four nucleotide triphosphates and Mg++ and produces a product which is DNase sensitive and RNase resistant.
Abstract: A technique has been developed allowing the autoradiographic detection of incorporation of 3H-thymidine-5′-triphosphate (3H-TTP) into nuclear DNA of smears of Sarcoma-180 (S-180) mouse ascites tumors under the direction of the cell's own nuclear DNA polymerase. Dried smears are dipped into an agar solution, which strips cytoplasm from the nuclei, and are then air dried and incubated with a buffered mixture containing four nucleotide triphosphates (one labeled), Mg++, and Ficoll, with the cell's own DNA acting as primer. The incorporation of 3H-TTP into the nuclei, like the cell free DNA polymerase assay, is largely dependent on the presence of all four nucleotide triphosphates and Mg++ and produces a product which is DNase sensitive and RNase resistant. DNA polymerase activity, as studied in a cell free assay, decreases with tumor age. This correlates well with a decreasing 3H-TTP labeling index in autoradiographs of aging tumors. The 3H-TTP labeling index has also been shown to exceed but parallel the in vivo3H-thymidine (3H-TdR) pulse labeling index for all tumor ages examined. In at least some cell systems DNA polymerase seems characteristic of cells in cycle. The autoradiographic detection of nuclei containing the enzyme offers a new tool for the study of tumor cytokinetics.

Journal ArticleDOI
07 Nov 1973-Heredity
TL;DR: Crosses and backcrosses made between a plastic flax variety and a non-plastic linseed variety were tested for plasticity by determining whether changes in amount of nuclear DNA are induced in them when grown in the specific inducing environments of nitrogen and phosphorus.
Abstract: Varieties of flax in which heritable changes can be induced by growing the plants in different environments are called plastic varieties. Large differences in plant weight and in amount of nuclear DNA can be induced in them. Other varieties are non-plastic either because they are genetically different or because their ancestral environments have stabilised them, or for both reasons. Crosses and backcrosses made between a plastic flax variety (Pl) and a non-plastic linseed variety (R) were tested for plasticity by determining whether changes in amount of nuclear DNA are induced in them when grown in the specific inducing environments of nitrogen and phosphorus. Pl was found to contain a nuclear factor and a cytoplasmic factor both of which must be present for the plastic character to appear. R contains neither of these factors but it has sites, in common with Pl, at which changes in amount of nuclear DNA occur when the Pl nuclear and cytoplasmic factors are introduced. These genetic elements can be formally separated into regulator and structural genes. A varietal DNA difference between Pl and R of about 2·8 per cent, does not show a consistent pattern of inheritance in the different types of crosses, either because of the inducing treatments or because of other interactions between the genotypes.

Journal ArticleDOI
TL;DR: The heavy satellite sequences identified in DNA from P. c.
Abstract: DNA from Plethodon cinereus cinereus separates into two fractions on centrifugation to equilibrium in neutral CsCl The smaller of these fractions has been described as a high-density satellite It represents about 2% of nuclear DNA from this species, and it has a density of 1728 g/cm3 It is cytologically localized near the centromeres of all 14 chromosomes of the haploid set In P c cinereus the heavy satellite DNA constitutes about 1/4 of the DNA in centromeric heterochromatin The nature of the rest of the DNA in centromeric heterochromatin is unknown The number of heavy satellite sequences clustered around the centromeres in a chromosome from P c cinereus is roughly proportional to the size of the chromosome, as determined by in situ hybridization with satellite-complementary RNA, and autoradiography Likewise the amount of contromeric heterochromatin, as identified by its differential stainability with Giemsa, shows a clear relationship to chromosome size — The heavy satellite sequences identified in DNA from P c cinereus are also present in smaller amounts in other closely related forms of Plethodon Plethodon cinereus polycentratus and P richmondi have approximately half as many of these sequences per haploid genome as P c cinereus P hoffmani and P nettingi shenandoah have about 1/3 as many of these sequences as P c cinereus P c cinereus, P c polycentratus, and P richmondii all have detectable heavy satellites with densities of 1728 g/cm3 Among these forms, satellite size as determined by optical density measurements, and number of satellite sequences as determined from hybridization studies, vary co-ordinately P c cinereus heavy satellite sequences are not detectable in P nettingi, P n hubrichti, or P dorsalis The latter species has a heavy satellite with a density of 1718 g/cm3, representing about 8% of the genomic DNA, and two light satellites whose properties have not been investigated The heavy satellite of P dorsalis is cytologically localized in the centromeric heterochromatin of this species — These observations are discussed in relation to the function and evolution of highly repetitive DNA sequences in the centromeric heterochromatin of salamanders and other organisms