ribosomal DNA

Information about ribosomal DNA

Not to be confused with Reformed Druids of North America.
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Arrangement of eukaryotic 18S, 5.8S and 28S rDNA in a tandem repetitive cluster; the 5S rDNA is coded separately. NTS, nontranscribed spacer, ETS, external transcribed spacer, ITS, internal transcribed spacer.
Ribosomal DNA (rDNA) are sequences encoding ribosomal RNA. These sequences regulate amplification and transcription initiation and contain transcribed and nontranscribed spacer segments. The nucleolus consists of expanded chromosomal loops that carry transcriptional units encoding ribosomal RNA. These regions are called rDNA. The ribosomal RNA transcriptional units are clustered in tandem repeats. These rDNA regions are also called nucleolus organizer regions, as they give rise to the nucleolus. In the human genome there are 5 chromosomes with nucleolus organizer regions: chromosomes 13,14,15,21 and 22.

In some contexts, rDNA stands for recombinant DNA.

The low rate of polymorphism in the rDNA transcription unit allows characterization of the rDNA of each species using only a few specimens, and makes this DNA useful for interspecific comparisons. In addition, the different coding regions of the rDNA repeats usually show distinct evolution rates. As a result, this DNA can provide information about almost any systematic level.[1]

See Also

Notes

1. ^ Hillis DM and Dixon MT (1991) Ribosomal DNA: molecular evolution and phylogenetic inference. Quart Rev Biol 66:411-453.
The Reformed Druids of North America, or RDNA, was formed at Carleton College, Northfield, Minnesota, in 1963, and marked the start of the American branch of neo-druidism.
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A ribosome is a small, dense, functional structure found in most known cells that assemble proteins and polypeptides used in cell division. It catalyses the assembly of individual amino acids into polypeptide chains by reading messenger RNAs and binding amino acids that are
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Left: An RNA strand, with its nitrogenous bases. Right: Double-stranded DNA.]] Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers, which plays several important roles in the processes of translating genetic information from
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nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton (8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles]]

In cell biology, the nucleolus (plural nucleoli
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Nucleolus organizer region (NOR) is a chromosomal region around which the nucleolus forms. It is also called the "nucleolar organizer". The region contains several tandem copies of ribosomal RNA genes.

See also

  • Cell nucleus

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human genome is the genome of Homo sapiens, which is composed of 24 distinct pairs of chromosomes (22 autosomal + X + Y) with a total of approximately 3 billion DNA base pairs containing an estimated 20,000–25,000 genes.
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Recombinant DNA is a form of artificial DNA which is engineered through the combination or insertion of one or more DNA strands, thereby combining DNA sequences which would not normally occur together.
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Recombinant DNA is a form of artificial DNA which is engineered through the combination or insertion of one or more DNA strands, thereby combining DNA sequences which would not normally occur together.
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