Extrachromosomal circular nuclear rDNA in Euglena gracilis. 1985

P Ravel-Chapuis, and P Nicolas, and V Nigon, and O Neyret, and G Freyssinet

The presence of extrachromosomal nuclear ribosomal DNA (rDNA) in the unicellular alga Euglena gracilis has been established. This rDNA is circular. Each circle is 3.8 micron long and contains one rDNA unit. Oligomers are rare. Extrachromosomal rDNA is present in large amounts during the exponential phase of growth and appears less abundant during the stationary phase. It was found in all wild-type and mutant strains of Euglena examined. Our estimations suggest that rDNA in Euglena is mainly extrachromosomal. Research of extrachromosomal rDNA in spinach and Petunia was negative.

UI MeSH Term Description Entries
D002467 Cell Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed) Cell Nuclei,Nuclei, Cell,Nucleus, Cell
D004270 DNA, Circular Any of the covalently closed DNA molecules found in bacteria, many viruses, mitochondria, plastids, and plasmids. Small, polydisperse circular DNA's have also been observed in a number of eukaryotic organisms and are suggested to have homology with chromosomal DNA and the capacity to be inserted into, and excised from, chromosomal DNA. It is a fragment of DNA formed by a process of looping out and deletion, containing a constant region of the mu heavy chain and the 3'-part of the mu switch region. Circular DNA is a normal product of rearrangement among gene segments encoding the variable regions of immunoglobulin light and heavy chains, as well as the T-cell receptor. (Riger et al., Glossary of Genetics, 5th ed & Segen, Dictionary of Modern Medicine, 1992) Circular DNA,Circular DNAs,DNAs, Circular
D004275 DNA, Ribosomal DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA. Ribosomal DNA,rDNA
D005056 Euglena gracilis A species of fresh-water, flagellated EUKARYOTES in the phylum EUGLENIDA. Euglena gracili,gracilis, Euglena
D005111 Extrachromosomal Inheritance Vertical transmission of hereditary characters by DNA from cytoplasmic organelles such as MITOCHONDRIA; CHLOROPLASTS; and PLASTIDS, or from PLASMIDS or viral episomal DNA. Cytoplasmic Inheritance,Extranuclear Inheritance,Inheritance, Cytoplasmic,Inheritance, Extrachromosomal,Inheritance, Extranuclear
D005796 Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Cistron,Gene,Genetic Materials,Cistrons,Genetic Material,Material, Genetic,Materials, Genetic
D012335 RNA, Ribosomal The most abundant form of RNA. Together with proteins, it forms the ribosomes, playing a structural role and also a role in ribosomal binding of mRNA and tRNAs. Individual chains are conventionally designated by their sedimentation coefficients. In eukaryotes, four large chains exist, synthesized in the nucleolus and constituting about 50% of the ribosome. (Dorland, 28th ed) Ribosomal RNA,15S RNA,RNA, 15S

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