Showing papers on "Nuclear DNA published in 1979"
TL;DR: The rate of evolution of the mitochondrial genome appears to exceed that of the single-copy fraction of the nuclear genome by a factor of about 10 and is likely to be an extremely useful molecule to employ for high-resolution analysis of the evolutionary process.
Abstract: Mitochondrial DNA was purified from four species of higher primates (Guinea baboon, rhesus macaque, guenon, and human) and digested with 11 restriction endonucleases. A cleavage map was constructed for the mitochondrial DNA of each species. Comparison of the maps, aligned with respect to the origin and direction of DNA replication, revealed that the species differ from one another at most of the cleavage sites. The degree of divergence in nucleotide sequence at these sites was calculated from the fraction of cleavage sites shared by each pair of species. By plotting the degree of divergence in mitochondrial DNA against time of divergence, the rate of base substitution could be calculated from the initial slope of the curve. The value obtained, 0.02 substitutions per base pair per million years, was compared with the value for single-copy nuclear DNA. The rate of evolution of the mitochondrial genome appears to exceed that of the single-copy fraction of the nuclear genome by a factor of about 10. This high rate may be due, in part, to an elevated rate of mutation in mitochondrial DNA. Because of the high rate of evolution, mitochondrial DNA is likely to be an extremely useful molecule to employ for high-resolution analysis of the evolutionary process.
3,199 citations
TL;DR: Analysis of newly replicated viral DNA shortly after the onset of viral DNA synthesis, the progeny DNA accumulating in the nuclei late in infection, and rapidly sedimenting DNA present in nuclei of infected cells at 8 h after infection are reported.
Abstract: Previous reports (H. Delius and J. B. Clements, J. Gen. Virol. 33 :125-134, 1976; G. S. Hayward, R. J. Jacob, S. C. Wadsworth, and B. Roizman, Proc. Natl. Acad. Sci. U.S.A. 72 :4243-4247, 1975; B. Roizman, G. S. Hayward, R. Jacob, S. W. Wadsworth, and R. W. Honess, Excerpta Med. Int. Congr. Ser. 2 :188-198, 1974) have shown that herpes simplex virus DNA extracted from virions accumulating in the cytoplasm of infected cells consists of four populations of linear molecules differing in the orientation of the covalently linked large (L) and small (S) components relative to each other. Together, these four isomeric arrangements of viral DNA display four different termini and four different L-S component junctions. In the studies reported in this paper, we analyzed with restriction endonucleases the newly replicated viral DNA shortly after the onset of viral DNA synthesis, the progeny DNA accumulating in the nuclei late in infection, and rapidly sedimenting DNA present in nuclei of infected cells at 8 h after infection. In each instance the nuclear viral DNA contained a decreased concentration of all four terminal fragments and an increase in the concentration of fragments spanning the junction of L and S components relative to the concentration of other DNA fragments. The results are consistent with the hypothesis that the viral DNA accumulating in the nuclei consists of head-to-tail concatemers arising from the replication of DNA by a rolling-circle mechanism. A model is presented for generation of all four isomeric arrangements of herpes simplex virus DNA from one arrangement based on excision and repair of unit length DNA from head-to-tail concatemers and known features of the sequence arrangement of viral DNA. Images
240 citations
TL;DR: The DNA from two transplantable hepatocellular carcinoma lines was less methylated than predicted rates of cell division in these tumors, suggesting that an aberration in endogenous DNA methylation may occur during neoplastic transformation.
172 citations
TL;DR: Mitochondrial (Mt) DNA from Podospora anserina was isolated and characterized with respect to density in CsCl, contour length and endonuclease restriction enzymes, and each of the four races examined had a characteristic fragment pattern.
Abstract: Mitochondrial (Mt) DNA from Podospora anserina was isolated and characterized with respect to density in CsCl, contour length and endonuclease restriction enzymes. The density of Mt DNA for four races examined was 1.694 g/cm3, compared with 1.712 g/cm3 for nuclear DNA. Extraction in the presence of a nuclease inhibitor, aurintricarboxylic acid and isolation in DAPI CsCl gradients allowed us to isolate high molecular weight DNA. Mt DNA isolated by total DNA extraction contained ca. 1% of circular molecules, 31 μm in contour length; Mt DNA isolated from purified mitochondria contained 2–4% of these 31 μm circles. Analysis with Eco RI restriction endonuclease revealed that each of the four races examined, s, A, T and E had a characteristic fragment pattern. Races s and A Mt DNA differed by only one fragment after Eco RI enzymatic digestion; similarly, these two DNA differed by only one or two fragments after Hae III digestion.
124 citations
TL;DR: Analysis of CsCl profiles and melting patterns suggested that mitochondrial DNA contains interspersed (A + T)-rich sequences.
110 citations
TL;DR: A recombinant plasmid is constructed containing approximately half the DNA sequence coding for a Trypanosoma brucei variable antigen and inserted sequences to various restriction enzyme digests of nuclear DNA from different trypanosome clones, showing differences in the sizes of restriction fragments hybridising to the inserted variable antigen coding sequence.
Abstract: The capacity of African trypanosomes to express sequentially a large repertoire of different surface antigens during an infection enables the parasite to evade the immune response of its host, and makes attempts to produce a vaccine against the disease difficult. It is evident that point mutations cannot account for antigen diversity. Variable antigens like immunoglobulins are derived from an extensive family of genes of which only one is expressed in a given cell. As somatic tic recombination is involved in the immunoglobulin gene system, this similarity prompted us to search for somatic rearrangements in trypanosome variable antigen genes. We have constructed a recombinant plasmid containing approximately half the DNA sequence coding for a Trypanosoma brucei variable antigen and hybridised the inserted sequences to various restriction enzyme digests of nuclear DNA from different trypanosome clones. Differences in the sizes of restriction tion fragments hybridising to the inserted variable antigen coding sequence show altered positions of enzyme sites relative to this sequence, indicating different arrangements of DNA sequences around this gene in different trypanosome clones.
110 citations
TL;DR: This chapter focuses on the visualization of yeast mitochondrial DNA dna with the fluorescent stain “DAPI,” which is a most effective stain for yeast nuclear DNA and for DNA in a variety of other organisms.
Abstract: Publisher Summary This chapter focuses on the visualization of yeast mitochondrial DNA dna with the fluorescent stain “DAPI.” DAPI stains AT-rich yeast mitochondrial DNA very strongly, it is not specific for these molecules, and it is a most effective stain for yeast nuclear DNA and for DNA in a variety of other organisms. The chapter outlines a method that may form the basis of suitable procedures for these other applications. The chapter also provides an overview on staining methods such as postvital staining, vital staining, and microscopy. Fading is not a serious problem with DAPI, because it takes several minutes for the intensity of the fluorescent image to decline to an intolerable level. Such fading as does occur seems to be reduced if the stained cells are washed and mounted in water.
90 citations
TL;DR: The supplementary DNA fraction which distinguishes outbreeding from inbreeding species has, at most, surprisingly little effect upon the growth and development of the Lolium hybrids.
Abstract: Inbreeding species of Lolium have about 40 per cent more nuclear DNA than the outbreeding species. Even so inbreeders may be readily hybridised with outbreeders to produce viable F1's which, in many cases, are fertile, producing F2 progenies on intercrossing or backcross progenies when crossed with the parents. Recombination between and within chromosomes at meiosis in the F1 results in the quantitative segregation of DNA to the nuclei of gametes and of F2 and backcross progenies. An assay of the effects of the DNA variation among these progenies showed no influence of DNA amount upon the expression of 19 phenotypic characters, ranging from early seedling growth to flowering. There was, however, a very slight reduction from expectation in the mean DNA amount of backcross and F2 progenies. Apart from this slight effect on viability, either of gametes or of zygotes with high nuclear DNA content, our assay shows that the supplementary DNA fraction which distinguishes outbreeding from inbreeding species has, at most, surprisingly little effect upon the growth and development of the Lolium hybrids.
69 citations
TL;DR: The rad7, rad14 and mms19 mutants were found to be defective in their ability to remove UV-induced dimers from nuclear DNA.
Abstract: The ability to remove ultraviolet (UV)-induced pyrimidine dimers from the nuclear DNA of yeast was examined in two radiation-sensitive (rad) mutants and one methyl methanesulfonate-sensitive (mms) mutant of the yeast Saccharomyces cerevisiae. The susceptibility of DNA from irradiated cells to nicking by an endonuclease activity prepared from crude extracts of Micrococcus luteus was used to measure the presence of dimers in DNA. The rad7, rad14 and mms19 mutants were found to be defective in their ability to remove UV-induced dimers from nuclear DNA. All three mutants belong to the same epistatic group as the other mutants involved in excision-repair. All three mutants show enhanced UV-induced mutations. The rad14 mutant also shows epistatic interactions with genes in the other two UV repair pathways.
66 citations
TL;DR: Binding assays to E. coli ribosomes indicate that tRNA2Thrrecognizes the threonine triplet ACA and may also recognize the other three triplets but with a much lower efficiency.
Abstract: 1. Mitochondria of Saccharomyces cerevisiae contain two tRNA's that are acylated with threonine. The two isoaccepting species (tRNA1Thr and tRNA2Thr) can be separated by reversed-phase chromatography on RPC-5. 2. A cytoplasmic mutant has been isolated which lacks tRNA1Thr but has normal levels of tRNA2Thr. This mutation was previously shown to map between the oxi 1 and oxi 2 loci on mitochondrial DNA. 3. tRNA1Thr and tRNA2Thr hybridize to wild type mitochondrial but not nuclear DNA and are capable of partially competing with each other. Hybridization of each species to different segments of mitochondrial DNA isolated from p- clones indicate that there are two threonyl tRNA genes. One gene is located between oxi 1 and oxi 2 and codes for tRNA1Thr. The second gene codes for tRNA2Thr and is near the cap locus. 4. Binding assays to E. coli ribosomes indicate that tRNA2Thr recognizes the threonine triplet ACA and may also recognize the other three triplets but with a much lower efficiency. None of the four codons for threonine stimulate the binding of tRNA1Thr to the ribosomes.
66 citations
TL;DR: A small percentage of human fibroblast cells survived high-multiplicity infection by cytomegalovirus and were isolated as persistently infected cultures and found that nuclei from nonproductive cells contained a significant amount of viral DNA that was distributed in most of these cells.
Abstract: A small percentage of human fibroblast cells survived high-multiplicity infection by cytomegalovirus and were isolated as persistently infected cultures. Approximately 30% of the cells were in the productive phase of infection, since virus-specific structural antigens and virions were associated with these cells. The remaining cells contained neither viral structural antigens nor particles. Nuclear DNA from these nonproductive cells contained approximately 120 genome equivalents of viral DNA per cell as determined by reassociation kinetics. In situ hybridization confirmed that nuclei from nonproductive cells contained a significant amount of viral DNA that was distributed in most of these cells. Early virus-induced proteins and antigens were also detected. Nonproductive cells continued to grow, and there was a slow, spontaneous transition of some of these cells to productive viral replication. The majority of the viral DNA in nonproductive cells persisted with restricted gene expression. When infectious virus production was eliminated by growing the persistently infected cultures in the presence of anticytomegalovirus serum, approximately 45 genome equivalents of the viral DNA persisted per cell. The reassociation reaction approached completion. After removal of the antiserum and subculturing, infectious virus production resumed. Therefore, it was assumed that all sequences of the viral genome remained associated with these cells. Restriction of cytomegalovirus gene expression in persistently infected cell cultures is discussed.
01 Jan 1979
TL;DR: DNA contents once more establish the close relationship of the S. nivalis subgroup with the taxa formerly classified under Chionodoxa, viz.
Abstract: The amounts of nuclear DNA and constitutive heterochromatin have been determined in 18 species of the Scilla bifolia group. and in the less closely related. S. messeniaca and S. siberica. Together with morphological criteria these data allow to reconstruct the pathways of chromosome evolution in the S. bifolia group at the diploid level with considerable accuracy. A progressive decrease of the DNA content by a factor of 0.5 occurred during the evolution from primitive yellow-seeded (S. kladnii: 1C = 8.6 pg) to advanced black-seeded species (e.g. S. luciliae: 1C = 4.3 pg). Grey- and brown-seeded species correspond to intermediary evolutionary stages and have intermediate DNA contents. 14 of 18 species have low amounts of heterochromatin (appr. 4%) irrespective of DNA content. However, two separate evolutionary side-branches are characterized by the accumulation of C-band material (3 yellow-seeded and 1 black-seeded species). The data suggest that an incipient DNA increase due to heterochromatin addition occurred in both instances. Further speciation in the yellow-seeded branch was accompanied by a decrease of total DNA despite of an increase in C-band content.—DNA contents once more establish the close relationship of the S. nivalis subgroup with the taxa formerly classified under Chionodoxa, viz. the S. luciliae subgroup.— The systematic position of S. messeniaca (x = 9) next to the S. bifolia group, previously suggested for reasons of morphology and chromosome number, is now supported by the DNA amount (1C = 10.7 pg). S. siberica (x = 6) as a remote relative contains considerably more DNA (1C = 31.7 pg).
TL;DR: The kinetics of the association of these cDNAs with nuclear DNA from rat liver, rat kidney, and Morris hepatoma 7777 under conditions of vast DNA excess indicated that the albumin and AFP mRNA's are transcribed from "nonrepetitive DNA."
Abstract: Full-length radiolabeled albumin and alpha-fetoprotein (AFP) cDNAs were synthesized from pure albumin and AMP mRNA preparations by using avian myeloblastosis virus reverse transcriptase (RNA-dependent DNA polymerase). The cDNAs have been used to quantitate the number of albumin and AFP genes in different rat tissues by two independent methods, both of which yielded similar results. First, the kinetics of the association of these cDNAs with nuclear DNA from rat liver, rat kidney, and Morris hepatoma 7777 under conditions of vast DNA excess indicated that the albumin and AFP mRNA's are transcribed from "nonrepetitive DNA." Second, saturation hybridization experiments in which a constant amount of rat liver DNA or Morris hepatoma 7777 was hybridized with increasing amounts of cDNA to albumin mRNA have shown the presence of 1--2 albumin genes per rat haploid genome. The number of AFP genes obtained in similar titration experiments was approximately 2--3. This was true whether rat liver DNA or hepatoma 7777 DNA was used in the reassociation experiments. When high molecular weight DNA preparations from both these tissues were digested with the restriction endonuclease EcoRI and the fragments were transferred to a nitrocellulose filter, the albumin and AFP [32P]cDNA probes hybridized to different sets of DNA fragments. However, each probe gave the same hybridization pattern whether Buffalo rat liver DNA or hepatoma 7777 DNA was utilized.
TL;DR: The gross organization of chromatin is species-specific, but not tissue-specific and function-dependent, and the higher the DNA content the more the euchromatin remains in the condensed state during interphase, but to a lower coiling order than the heterochromatin.
Abstract: In contrast to mammalian cell nuclei those of plants display nearly an identical ultrastructure in all developmental stages and tissues. This indicates that the gross organization of chromatin is species-specific, but not tissue-specific and function-dependent. The species-specific nuclear ultrastructure is determined by the basic nuclear DNA content (2 C value). The higher the DNA content, the more the euchromatin remains in the condensed state during interphase, but to a lower coiling order than the heterochromatin. Some difficulties in the interpretation of electron micrographs of cell nuclei, and the possible role of repetitive DNA sequences in the karyotypical condensation of euchromatin in plants are discussed.
TL;DR: The 14C-labeled photosensitive monoazide analog of ethidium, 3-amino-8-azido-5-ethyl-6-phenylphenanthridinium chloride, produced covalent adducts in yeast cells with both nuclear and mitochondrial DNA on photolysis by visible light, which eliminated drug attached to nuclear DNA with conservation of DNA.
TL;DR: Two different classes of defective DNA derived from HSV-1 Angelotti (ANG) in independent series of high MOI-passages were studied and nucleotide sequences contained in the defective DNA were localized on the parental viral genome.
Abstract: During serial passages of Herpes simplex virus (HSV) at high multiplicity of infection, virions containing defective viral DNA accumulate in the progeny. The defective DNA molecules are made up by repeats of restricted portions of the standard viral genome. Two different classes of defective DNA derived from HSV-1 Angelotti (ANG) in independent series of high MOI-passages were studied. The nucleotide sequences contained in the defective DNA were localized on the parental viral genome. One of the two classes contained sequences from non-contiguous sites mapping in unique and in redundant regions of the parental DNA, whereas the second class apparently originates from the S-terminal redundant region of the parental DNA. The localization of defective DNA sequences was complicated by the fact that there exists sequence homology between the S-terminal redundancy and various unique DNA sequences in the L-segment of the HSV-1 ANG genome.
TL;DR: Advanced biochemical and biophysical techniques are used to differentiate cytoplasmic and cell surface deoxyribonucleic acids (DNA) from nuclear DNA and to counter the trivial argument that such DNA is a contaminant produced during the preparation.
Abstract: Publisher Summary Advanced biochemical and biophysical techniques are used to differentiate cytoplasmic and cell surface deoxyribonucleic acids (DNA) from nuclear DNA and to counter the trivial argument that such DNA is a contaminant produced during the preparation. The evidence from biochemistry and morphology indicates that three separate compartments exist for accommodation of cellular DNA—nuclear, cytoplasmic including the plasma membrane, and extracellular or excreted DNA. If these three compartments are a part of a covalently linked polymer system, as seems not unlikely, then an interchange possibly of great velocity among the compartments is equally as likely. It is possible in such a close-knit system that a rearrangement of the carbohydrate chains of surface glycoprotein would be inevitably accompanied by a rearrangement of the sequence of a nucleotide polymer formed on the surface at the time. Biochemical methods are concerned with cell fractionation studies using centrifugation in various media. They reveal that a varying but small fraction of the DNA is found in postmitochondrial fractions, which in different studies may or may not vary from the nuclear DNA in several respects, including molecular weight, specific activity, sensitivity to antimetabolites, melting profile, and buoyant density.
TL;DR: The result indicates that the increase in replicative flux of mtDNA is associated with the removal of a block in the conversion of D-loops to other intermediates, which would indicate that the purity of the mtDNA was assessed from its molecular conformation and by renaturation-kinetic analysis.
Abstract: We studied DNA (mtDNA) replication in adult female rat hearts undergoing hypertrophy secondary to constriction of the ascending aorta. MtDNA was measured in isolated mitochondria by a fluorometric method adapted for that purpose. The conditions for removal of contaminating nuclear DNA were developed, and the purity of the mtDNA was assessed from its molecular conformation (open and closed circles) and by renaturation-kinetic analysis. The mtDNA concentration in mitochondria, expressed as micrograms of DNA per milligram of mitochondrial protein, increased 2, 4, and 7 days postoperatively by 21, 73, and 98%, respectively. Similar results were obtained when mtDNA was expressed per nonomole of cytochrome a. The population of replicative intermediates of mtDNA was analyzed by electron microscopy. In normal hearts, we observed molecular forms characteristic of animal mtDNA, such as circular monomers and dimers, catenated molecules, D-loops, expanded D-loops, and gapped molecules. D-loop frequency, which was near 50% in the mtDNA of control hearts, was markedly reduced to 5-7% in hypertrophying hearts. This result indicates that the increase in replicative flux of mtDNA is associated with the removal of a block in the conversion of D-loops to other intermediates.
01 Jan 1979
TL;DR: In this article, the authors analyzed mitochondrial DNA samples from 21 individuals of diverse racial background using 8 restriction endonucleases and found that the mitochondrial DNA population from each individual appeared to be highly homogeneous, while some individuals were observed to differ from one another in their nucleotide sequence.
Abstract: Mitochondrial DNA can be obtained with relative ease from individuals. Multiple samples can be quickly analysed using gel electrophoretic analysis of restriction endonuclease digests of the DNA. Mitochondrial DNA samples from 21 humans of diverse racial background were analysed using 8 restriction endonucleases. The mitochondrial DNA population from each individual appeared to be highly homogeneous. By contrast, mitochondrial DNA from some of the individuals were observed to differ from one another in their nucleotide sequence. Fourteen of the 21 samples appeared identical to one another in the 64 restriction sites examined. The remaining seven samples differed at one or more restriction sites from the wild type and from each other. We calculate that mitochondrial DNA from randomly chosen pairs of humans will differ on an average at 65 base pairs per mitochondrial genome, or at one base pair out of 250. This degree of difference exceeds that observed in studies of vertebrate single copy nuclear DNA and is consistent with other evidence indicating that the rate of evolution of mitochondrial DNA is rapid. Mitochondrial DNA analyses will thus be especially valuable for studies of genetic variability within and among populations and among closely related species.
TL;DR: It is suggested that differential DNA replication and endopolyploidization may be basic factors in the complex mechanism of cell and tissue differentiation.
Abstract: The Feulgen-DNA content of 3558 nuclei from 21 different tissues and organs ofScilla decidua (Liliaceae) was measured by a scanning cytophotometer interfaced to a computer. The basic nuclear DNA content (2 C value) was 13.62 pg, and 71 per cent of the nuclei were polyploid. The highest DNA values were found in the antipodal cells of the ovule, and the elaiosomes of the seeds (512 C). In addition to polyploidy, the 2 C values exhibited tissue-specific variation which was statistically significant (0.05% level of probability), It is suggested that differential DNA replication and endopolyploidization may be basic factors in the complex mechanism of cell and tissue differentiation.
TL;DR: Quantitative analyses have shown that in mouse P815 cells, DNA of inverted repetitive sequences is methylated to a level about 50% higher than the normal repetitive DNA sequences and to about 300%Higher than the unique and intermediary intermediatry sequences.
Journal Article•
TL;DR: Ulastructural studies revealed a very close correlation between the dose-response curve for mitochondrial damage and that for MGBG inhibition of mitochondrial DNA synthesis, which suggests a direct cause-and-effect relationship between inhibition of mitochondria of proliferating cell populations and ultrastructureural damage.
Abstract: Methylglyoxal-bis(guanylhydrazone) (MGBG) is a polycationic drug which is useful in the chemotherapy of lymphoid and myeloid proliferative disorders. The drug has recently been shown to produce selective ultrastructural damage to the mitochondria of proliferating cell populations. It is important to understand the molecular basis for this action, since it may be related to the known ability of MGBG to block polyamine biosynthesis. Accordingly, the effect of MGBG treatment on the incorporation of [ 3 H]thymidine into both mitochondrial and nuclear DNA has been examined. Exponentially growing L1210 leukemia cells were prelabeled with [ 14 C]thymidine, treated with MGBG for 1.5 to 16 hr, and then pulse labeled with [ 3 H]thymidine. Incorporation of [ 3 H]thymidine into mitochondrial DNA was selectively inhibited at 5 hr with concentrations of 1 to 10 µm MGBG. Nuclear DNA, however, was not similarly affected until 8 to 11 hr of drug treatment. Dye-CsCl gradients of mitochondrial DNA indicated that the inhibition of synthesis occurred in replicative forms of circular DNA. Uptake studies excluded the possibility of drug interference with cellular uptake of thymidine. Ultrastructural studies revealed a very close correlation between the dose-response curve for mitochondrial damage and that for MGBG inhibition of mitochondrial DNA synthesis. This correlation suggests a direct cause-and-effect relationship between inhibition of mitochondrial DNA synthesis and ultrastructural damage, but the possibility of both phenomena being related to another action by the drug, such as inhibition of polyamine biosynthesis, or a drug effect on mitochondrial function, must also be considered.
TL;DR: Observations suggest that the different segments of Physarum DNA from which foldback structures are derived contain nucleotide sequences that share a highly ordered and unform pattern of structural organisation.
Abstract: Inverted repeat sequences, capable of forming stable intra-chain foldback duplexes, are shown using electron microscopy to be located in over 90% of fragments of nuclear DNA from Physarum polycephalum. A statistical treatment of the data indicates that, on average, foldback sequence foci are spaced every 7,000 nucleotides and that they are distributed uniformly amongst the DNA chains. The majority of inverted repeat sequences give rise to the simple types of foldback structure observed in DNA from other eukaryotic species, but a significant proportion of the DNA fragments also contain novel foldback structures with a more complex appearance, referred to as 'bubbled' hairpins. The latter structures appear to be formed by the annealing of several distinct segments of homologous inverted repeat sequence, each separated by interspersed non-foldback sequences of variable sizes up to 15,000 nucleotides in length. The size, both of the foldback duplexes and of the intervening single-chain segments of DNA, are not random. Instead, they appear to form a regular, arithmetic series of lengths. These observations suggest that the different segments of Physarum DNA from which foldback structures are derived contain nucleotide sequences that share a highly ordered and unform pattern of structural organisation. These regular units of organisation in Physarum DNA in some cases extend over distances up to 50,000 nucleotides in length.
TL;DR: The results suggest that the level of nuclear DNA polymerase α has close relation to the ts defect of this Dna − mutant, which shows no increase in cell number and rapid decrease in the rate of DNA synthesis after temperature upshift.
TL;DR: The relative DNA content was measured using the cytofluorometric technique in isolated nuclei over different intervals after synchronous divisions to suggest that some part of the DNA is replicated in interphase more than once and not all nuclear DNA of the maternal cell is transmitted to the nuclei of daughter cells during mitosis.
TL;DR: A population of small covalently closed non-mitochondrial circular DNA molecules was isolated from the petite-negative yeast Schizosaccharomyces pombe and disappearance after DNase treatment of mitochondria demonstrates their extramitochondrial location.
Abstract: A population of small covalently closed non-mitochondrial circular DNA molecules was isolated from the petite-negative yeast Schizosaccharomyces pombe. The mean length of these molecules, possessing the same density as nuclear DNA (1.695 g/ cm3) is 1.95±0.18 μm. The presence of these minicircles in crude mitochondrial preparations indicates their tight association with mitochondrial particles. Their disappearance after DNase treatment of mitochondria demonstrates their extramitochondrial location.
TL;DR: The chapter discusses that the contribution of the nuclear DNA to the respiratory competence of mitochondria includes structural and regulatory genes for the matrix enzymes, the DNA replication and transcription systems, and the proteins of the ribosomes, the F 1 ATPase, and certain subunits of the respiratory enzyme complexes.
Abstract: Publisher Summary This chapter reviews the biogenesis of respiratory competent mitochondria in the yeast Saccharomyces cerevisiae that is dependent on the function of both mitochondrial and nuclear genes. Mitochondrial DNA includes genes that determine and/or regulate the biosynthesis of subunit polypeptides of the respiratory enzymes cytochrome oxidase and coenzyme QH 2 -cytochrome C reductase and of the oligomycin-sensitive ATPase. It is known that mitochondrial DNA contains genes that code for the ribosomal RNA's and transfer RNA's of the mitochondrial protein synthetic machinery. These are known as “syn genes.” The chapter discusses that the contribution of the nuclear DNA to the respiratory competence of mitochondria includes structural and regulatory genes for the matrix enzymes, the DNA replication and transcription systems, and the proteins of the ribosomes, the F 1 ATPase, and certain subunits of the respiratory enzyme complexes. Strains that carry nuclear mutations resulting in an inability to use nonfermentable substrates for growth are called “pet mutants.” Mutant isolation procedures described in the chapter are designed to select mutants with specific defects in mitochondrial functions. They include (1) pet mutants with specific lesions in the respiratory enzymes or the ATPase, (2) mit – mutants with lesions in cytochrome oxidase, coenzyme QH 2 -cytochrome C reductase or oligomycin-sensitive ATPase, and (3) syn– mutants specifically defective in mitochondrial protein synthesis.
TL;DR: Five nuclear mutants enhancing the spontaneous mutation rate of mtDNA have been isolated in Saccharomyces cerevisiae and indicate that at least two common steps control both nuclear DNA repair and the mutability of particular alleles of the mtDNA.
Abstract: Five nuclear mutants enhancing the spontaneous mutation rate of mtDNA have been isolated in Saccharomyces cerevisiae. These mutators fall into five complementation groups and are located at five genetic loci different from rad50 to rad57 loci. Three mutants (gam1, gam2, and gam4), insensitive or weakly sensitive to gamma-rays, exhibit increased frequency of spontaneous production of mutants with large deletions of the mtDNA (p-) and of all tested mitochondrial drug-resistant mutants. Two other mutants (gam3 and gam5), highly sensitive to gamma-rays, increase only the mutation rate of particular alleles of the mtDNA. The mutant gam5 enhances only the production of p- and erythromycin-resistant clones. The mutant gam3 exhibits an enhanced rate of oligomycin-resistant clones as well as a collateral increase of nuclear mutability. The existence of gam3 and gam5 mutants indicates that at least two common steps control both nuclear DNA repair and the mutability of particular alleles of the mtDNA. However, the general spontaneous mutability of the mtDNA includes at least three steps not involved in the repair of nuclear DNA, as revealed by the gam1, gam2, and gam4 mutations.
TL;DR: Scanning cytophotometric measurements in vegetative and reproductive buds of Rhoeo discolor revealed a transitory increase in staining intensity in more than half of the cells in early differentiating floral buds, suggesting that the different Feulgen extinction values reflect different nuclear DNA amounts.
TL;DR: It has been shown that the two ancient tetraploids Cyprinus carpio and Thymallus thymallu are, with regard to the thermal stability of reassociated non-repetitive DNA, and with regards to the correspondence of reaction rates with the values expected for single copy DNA, indistinguishable from diploid controls.
Abstract: Non-repetitive DNA of anciently tetraploid teleostean species was analysed for the presence of duplicated sequences. Closely related diploid species were investigated in comparison. From the reassociation kinetics of total nuclear DNA, rate constants and fraction sizes of classes of repetitive and non-repetitive sequences were determined. DNA fractions enriched in the slowest renaturing sequence class were prepared and subjected to reassociation. The rate constants of these reactions were compared with the values expected for single-copy DNA from analytical genome size determinations. From reassociated DNA enriched in non-repetitive sequences also the melting temperatures were determined as a measure of internal base sequence heterogeneity. It has been shown that the two ancient tetraploids Cyprinus carpio and Thymallus thymallus are, with regard to the thermal stability of reassociated non-repetitive DNA, and with regard to the correspondence of reaction rates with the values expected for single copy DNA, indistinguishable from diploid controls (Rutilus rutilus, Clupea harengus and Sprattus sprattus). The tetraploid species Salmo irideus, Salvelinus fontinalis and Coregonus lavaretus appear as very recent tetraploids with regard to these criteria. The significance of the results for estimating the time of occurence of polyploidisation events in these taxa is discussed.