Biomaterial Database

Free ribosomal RNA genes in Paramecium are tandemly repeated. 1978

R C Findly, and J G Gall

The genes coding for 17S and 25S rRNA in Paramecium tetraurealia were isolated. The macronuclear ribosomal DNA (rDNA) exists as relatively small, extrachromosomal molecules with both linear and circular forms. Electron microscopy and restriction endonuclease analysis revealed that the rDNA is arranged as tandem repeats with an average repeat size of 5.5 X 10(6) daltons. Some heterogeneity of repeat lengths was found both by electron microscopy and by restriction enzyme analysis. The rDNA does not snap back after denaturation. This study provides additional evidence that extrachromosomal rDNA may be a common feature among lower eukaryotes. However, in contrast to several other cases, the rDNA of Paramecium is not palindromic, but occurs as tandem repeats as in higher eukaryotes.

UI	MeSH Term	Description	Entries
D008040	Genetic Linkage	The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME.	Genetic Linkage Analysis,Linkage, Genetic,Analyses, Genetic Linkage,Analysis, Genetic Linkage,Genetic Linkage Analyses,Linkage Analyses, Genetic,Linkage Analysis, Genetic
D010247	Paramecium	A genus of ciliate protozoa that is often large enough to be seen by the naked eye. Paramecia are commonly used in genetic, cytological, and other research.	Parameciums
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
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
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
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