scholarly journals SINGLE STRAND-CONTAINING REPLICATING MOLECULES OF CIRCULAR MITOCHONDRIAL DNA

1973 ◽  
Vol 56 (1) ◽  
pp. 230-245 ◽  
Author(s):  
David R. Wolstenholme ◽  
Katsuro Koike ◽  
Patricia Cochran-Fouts
Keyword(s):  
Mitochondrial Dna ◽  
Single Strand ◽  
Molecular Forms ◽  
Contour Length ◽  
Chick Embryos ◽  
Single Stranded Region ◽  
Mitochondrial Dnas ◽  
Replicative Intermediates ◽  
Circular Contour ◽  
Protein Monolayer

Mitochondrial DNAs (mtDNAs) from Chang rat solid hepatomas and Novikoff rat ascites hepatomas were examined in the electron microscope after preparation by the aqueous and by the formamide protein monolayer techniques. MtDNAs from both tumors were found to include double-forked circular molecules with a form and size suggesting they were replicative intermediates. These molecules were of two classes. In molecules of one class, all three segments were apparently totally double stranded. Molecules of the second class were distinguished by the fact that one of the segments spanning the region between the forks in which replication had occurred (the daughter segments) was either totally single stranded, or contained a single-stranded region associated with one of the forks. Daughter segments of both totally double-stranded and single strand-containing replicating molecules varied in length from about 3 to about 80% of the circular contour length of the molecule. Similar classes of replicating molecules were found in mtDNA from regenerating rat liver and chick embryos, indicating them to be normal intermediates in the replication of mtDNA All of the mtDNAs examined included partially single-stranded simple (nonforked) circular molecules. A possible scheme for the replication of mtDNA is presented, based on the different molecular forms observed

scholarly journals EVIDENCE FOR DISCONTINUOUS REPLICATION OF CIRCULAR MITOCHONDRIAL DNA MOLECULES FROM NOVIKOFF RAT ASCITES HEPATOMA CELLS

1974 ◽  
Vol 61 (1) ◽  
pp. 14-25 ◽  
Author(s):  
Katsuro Koike ◽  
David R. Wolstenholme
Keyword(s):  
Mitochondrial Dna ◽  
Hepatoma Cells ◽  
Single Strand ◽  
Contour Length ◽  
Rat Tissues ◽  
Ascites Hepatoma ◽  
Mean Values ◽  
Mitochondrial Fractions ◽  
Rat Ascites Hepatoma ◽  
Replicative Intermediates

Double-forked circular molecules of mitochondrial DNA (mtDNA) from rat tissues, indicated by their form and size to be replicative intermediates, are of two structurally distinct classes. Molecules of the first class are totally double stranded. Molecules of the second class are defined by one daughter segment being totally or partially single stranded. Length histograms of daughter segments measuring between 2% and 44% of the total 5-µm molecular contour were constructed from samples of both classes of replicating molecules derived from mtDNA or Novikoff rat ascites hepatoma cells. For single strand-containing molecules, the lengths fell into eight distinct, reproducible groups with mean values separated by 4.1–7.6% of the circular contour length. For totally double stranded molecules, the lengths fell into seven groups, corresponding to seven of the groups found for single strand-containing molecules. These results suggest that along at least 44% of the contour of mtDNA molecules there exist discrete points at which DNA synthesis tends to be arrested. This may indicate that there are pauses in normal mtDNA synthesis. However, as the DNA used in these experiments was isolated from mitochondrial fractions, the findings may indicate that continuation of synthesis beyond specific points on the nucleotide strands requires a factor which is not available after cell disruption.

Mitochondrial DNA from 4-Cell Stages of Ascaris Lumbricoides

1974 ◽  
Vol 16 (3) ◽  
pp. 593-601
Author(s):  
H. TOBLER ◽  
C. GUT
Keyword(s):  
Electron Microscopy ◽  
Mitochondrial Dna ◽  
Ascaris Lumbricoides ◽  
Buoyant Density ◽  
Contour Length ◽  
Cell Stage ◽  
Replicative Intermediates ◽  
Dna Amounts

Mitochondrial DNA (mtDNA) has been isolated from 4-cell stages of Ascaris lumbricoides. This DNA amounts to about 40% of the total quantity of 4-cell-stage DNA. Its buoyant density in neutral CsCl gradients is 1.686 g cm-3. Electron microscopy of mtDNA demonstrated the presence of circular molecules with an average contour length of 4.64 µm. About 15% of these molecules are supercoiled, covalently closed circles, whereas some 2% consist of double-forked circular molecules. The form and size of these branched molecules suggest that they are replicative intermediates.

Existence of DNA in yeast microbodies

1978 ◽  
Vol 36 (2) ◽  
pp. 232-233
Author(s):  
Masako Osumi ◽  
Misuzu Nagano ◽  
Hiroko Kazama
Keyword(s):  
Catalase Activity ◽  
Buoyant Density ◽  
Model System ◽  
Contour Length ◽  
Native State ◽  
Normal Alkane ◽  
Remarkable Increase ◽  
Dna Molecule ◽  
Mitochondrial Dnas

We have found that microbodies appeared profusely together with a remarkable increase in catalase activity in normal alkane-grown cells of hydrocarbon-utilizing Candida yeasts, and that the microbodies multiplied by division in these cells. These features of Candida yeasts seem to provide a useful model system for studies on the biogenesis of the microbody. Subsequently, we have succeeded in isolation of Candida microbodies in an apparently native state, as judged biochemically and morphologically. The presence of DNA in the purified microbody fraction thus obtained was proved by the diphenylamine method. DNA molecule of about 15 urn in contour length was released from an isolated microbody. The physicochemical analyses of the microbody DNA revealed that its buoyant density differed from nuclear and mitochondrial DNAs. All these results lead us to the possibility that there is a novel type of DNA in microbodies.

Nucleic Acid Molecules Prepared by Monolayer Techniques

1972 ◽  
Vol 30 ◽  
pp. 178-179
Author(s):  
Dimitrij Lang
Keyword(s):  
Electron Microscopy ◽  
Standard Deviation ◽  
Nucleic Acid ◽  
Cytochrome C ◽  
Nucleic Acids ◽  
Contour Length ◽  
Sample Standard Deviation ◽  
Molecular Weights ◽  
Length Measurements ◽  
Protein Monolayer

The success of the protein monolayer technique for electron microscopy of individual DNA molecules is based on the prevention of aggregation and orientation of the molecules during drying on specimen grids. DNA adsorbs first to a surface-denatured, insoluble cytochrome c monolayer which is then transferred to grids, without major distortion, by touching. Fig. 1 shows three basic procedures which, modified or not, permit the study of various important properties of nucleic acids, either in concert with other methods or exclusively:1) Molecular weights relative to DNA standards as well as number distributions of molecular weights can be obtained from contour length measurements with a sample standard deviation between 1 and 4%.

Assignment of two mitochondrially synthesized polypeptides to human mitochondrial DNA and their use in the study of intracellular mitochondrial interaction

1982 ◽  
Vol 2 (1) ◽  
pp. 30-41
Author(s):  
N A Oliver ◽  
D C Wallace
Keyword(s):  
Mitochondrial Dna ◽  
Restriction Site ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Synthesis ◽  
Human Mitochondrial Dna ◽  
Ht1080 Cells ◽  
Mitochondrial Dnas ◽  
A Cell ◽  
Dna Restriction ◽  
Restriction Site Polymorphisms

Two mitochondrially synthesized marker polypeptides, MV-1 and MV-2, were found in human HeLa and HT1080 cells. These were assigned to the mitochondrial DNA in HeLa-HT1080 cybrids and hybrids by demonstrating their linkage to cytoplasmic genetic markers. These markers include mitochondrial DNA restriction site polymorphisms and resistance to chloramphenicol, an inhibitor of mitochondrial protein synthesis. In the absence of chloramphenicol, the expression of MV-1 and MV-2 in cybrids and hybrids was found to be directly proportional to the ratio of the parental mitochondrial DNAs. In the presence of chloramphenicol, the marker polypeptide linked to the chloramphenicol-sensitive mitochondrial DNA continued to be expressed. This demonstrated that resistant and sensitive mitochondrial DNAs can cooperate within a cell for gene expression and that the CAP-resistant allele was dominant or codominant to sensitive. Such cooperation suggests that mitochondrial DNAs can be exchanged between mitochondria.

scholarly journals Intraspecific mitochondrial DNA polymorphism within the emerging filamentous fungal pathogen Trichoderma longibrachiatum

2006 ◽  
Vol 55 (1) ◽  
pp. 31-35 ◽  
Author(s):  
Zsuzsanna Antal ◽  
János Varga ◽  
László Kredics ◽  
András Szekeres ◽  
Lóránt Hatvani ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Fungal Pathogen ◽  
Internal Transcribed Spacer ◽  
Dna Polymorphism ◽  
Restriction Enzymes ◽  
Clinical Isolates ◽  
Trichoderma Longibrachiatum ◽  
Mitochondrial Dna Polymorphism ◽  
Mitochondrial Dnas ◽  
Dna Profiles

The genetic diversity of the emerging fungal pathogen Trichoderma longibrachiatum was examined at the level of mitochondrial DNA. The 17 investigated strains, comprising nine clinical and eight non-clinical isolates, exhibited seven and ten different mitochondrial DNA profiles by using the restriction enzymes BsuRI and Hin6I, respectively. The sizes of mitochondrial DNAs varied from 34·9 to 39·5 kb. The discriminatory power of the method was higher than that of internal transcribed spacer sequence analysis and therefore should be more suitable for identification and epidemiological investigations. However, clinical and non-clinical isolates did not form separate clusters on the resulting dendrogram and thus there was no indication of a correlation between genetic structure and pathogenicity of the isolates.

scholarly journals Genetic analysis of systematic mitochondrial heteroplasmy in rabbits.

Genetics ◽  
1994 ◽  
Vol 138 (2) ◽  
pp. 471-480 ◽  
Author(s):  
D Casane ◽  
N Dennebouy ◽  
H de Rochambeau ◽  
J C Mounolou ◽  
M Monnerot
Keyword(s):  
Mitochondrial Dna ◽  
Replication Origin ◽  
Molecular Diversity ◽  
Germ Line ◽  
Variable Number ◽  
The Other ◽  
Molecular Forms ◽  
Unusual Property ◽  
Mitochondrial Heteroplasmy ◽  
Selection For

Abstract One unusual property of rabbit mitochondrial DNA (mtDNA) is the existence of repeated 153-bp motifs in the vicinity of the replication origin of its H strand. Furthermore, every individual is heteroplasmic: it carries mtDNA molecules with a variable number of repeats. A systematic study of 8 females and their progeny has been devised to analyze mtDNA transmission through generations. The results suggest that three mechanisms are acting simultaneously. (1) Genetic drift in the germ line is revealed by the evolution of heteroplasmy when two major molecular forms are present in a female. (2) A high mutation rate (around 10(-2) per animal generation) generating molecular diversity, by deletion and addition of repeated units, is required to explain the observation of heteroplasmy in every individual. Moreover, the rates of mutation from the most frequent type to the other types are unequal. The deletion of one unit is more frequent than a deletion of two units, which is in turn more frequent than a deletion of three. (3) Selection for shorter molecules in somatic cells is probable. The frequency distribution of mtDNA types depends on the organ analyzed (kidney-spleen and liver vs. gonads).

scholarly journals The Complete Mitochondrial DNA of Trypanosoma cruzi: Maxicircles and Minicircles

2021 ◽  
Vol 11 ◽  
Author(s):  
Francisco Callejas-Hernández ◽  
Alfonso Herreros-Cabello ◽  
Javier del Moral-Salmoral ◽  
Manuel Fresno ◽  
Núria Gironès
Keyword(s):  
Mitochondrial Dna ◽  
Trypanosoma Cruzi ◽  
Present Species ◽  
Consensus Sequences ◽  
Conserved Sequence ◽  
Conserved Regions ◽  
Sequencing Technologies ◽  
Hypervariable Regions ◽  
Mitochondrial Dnas ◽  
Species Specific

The mitochondrial DNA of Trypanosomatids, known as the kinetoplast DNA or kDNA or mtDNA, consists of a few maxicircles and thousands of minicircles concatenated together into a huge complex network. These structures present species-specific sizes, from 20 to 40 Kb in maxicircles and from 0.5 to 10 Kb in minicircles. Maxicircles are equivalent to other eukaryotic mitochondrial DNAs, while minicircles contain coding guide RNAs involved in U-insertion/deletion editing processes exclusive of Trypanosomatids that produce the maturation of the maxicircle-encoded transcripts. The knowledge about this mitochondrial genome is especially relevant since the expression of nuclear and mitochondrial genes involved in oxidative phosphorylation must be coordinated. In Trypanosoma cruzi (T. cruzi), the mtDNA has a dual relevance; the production of energy, and its use as a phylogenetic marker due to its high conservation among strains. Therefore, this study aimed to assemble, annotate, and analyze the complete repertoire of maxicircle and minicircle sequences of different T. cruzi strains by using DNA sequencing. We assembled and annotated the complete maxicircle sequence of the Y and Bug2148 strains. For Bug2148, our results confirm that the maxicircle sequence is the longest assembled to date, and is composed of 21 genes, most of them conserved among Trypanosomatid species. In agreement with previous results, T. cruzi minicircles show a conserved structure around 1.4 Kb, with four highly conserved regions and other four hypervariable regions interspersed between them. However, our results suggest that the parasite minicircles display several sizes and numbers of conserved and hypervariable regions, contrary to those previous studies. Besides, this heterogeneity is also reflected in the three conserved sequence blocks of the conserved regions that play a key role in the minicircle replication. Our results using sequencing technologies of second and third-generation indicate that the different consensus sequences of the maxicircles and minicircles seem to be more complex than previously described indicating at least four different groups in T. cruzi minicircles.

Sign in / Sign up

Export Citation Format

Share Document