nucleotide

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nucleotide

(no͞o`klēətīd', nyo͞o`–), organic substance that serves as a monomer in forming nucleic acidsnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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. Nucleotides consist of either a purinepurine,
type of organic base found in the nucleotides and nucleic acids of plant and animal tissue. The German chemist Emil Fischer did much of the basic work on purines and introduced the term into the chemical literature in the early 20th cent.
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 or a pyrimidinepyrimidine
, type of organic base found in certain coenzymes and in the nucleic acids of plant and animal tissue. The three major pyrimidines of almost universal distribution in living systems are cytosine, thymine, and uracil.
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 base, a riboseribose
, monosaccharide carbohydrate of universal distribution in living tissue, found in ribonucleic acid (RNA; see nucleic acid), free nucleotides, and various coenzymes.
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 or deoxyribose, and a phosphate group. Adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
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 serves as the principle energy carrier for the cell's reactions. The most important nucleotides are those derived from the bases adenineadenine
, organic base of the purine family. Adenine combines with the sugar ribose to form adenosine, which in turn can be bonded with from one to three phosphoric acid units, yielding the three nucleotides adenosine monophosphate, adenosine diphosphate, and adenosine
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, guanineguanine
, organic base of the purine family. It was reported (1846) to be in the guano of birds; later (1879–84) it was established as one of the major constituents of nucleic acids.
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, cytosinecytosine
, organic base of the pyrimidine family. It was isolated from the nucleic acid of calf thymus tissue in 1894. A suggested structure for cytosine, published in 1903, was confirmed in the same year when that base was synthesized in the laboratory.
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, thyminethymine
, organic base of the pyrimidine family. Thymine was the first pyrimidine to be purified from a natural source, having been isolated from calf thymus and beef spleen in 1893–4.
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, and uraciluracil
, organic base of the pyrimidine family. It was isolated from herring sperm and also produced in a laboratory in 1900–1901. When combined with the sugar ribose in a glycosidic linkage, uracil forms a derivative called uridine (a nucleoside), which in turn can be
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.

Nucleotide

A cellular constituent that is one of the building blocks of ribonucleic acids (RNA) and deoxyribonucleic acid (DNA). In biological systems, nucleotides are linked by enzymes in order to make long, chainlike polynucleotides of defined sequence. The order or sequence of the nucleotide units along a polynucleotide chain plays an important role in the storage and transfer of genetic information. Many nucleotides also perform other important functions in biological systems. Some, such as adenosine triphosphate (ATP), serve as energy sources that are used to fuel important biological reactions. Others, such as nicotinamide adenine dinucleotide (NAD) and coenzyme A (CoA), are important cofactors that are needed to complete a variety of enzymatic reactions. Cyclic nucleotides such as cyclic adenosine monophosphate (cAMP) are often used to regulate complex metabolic systems. Chemically modified nucleotides such as fluoro-deoxyridine monophosphate (Fl-dUMP) contain special chemical groups that are useful for inactivating the normal function of important enzymes. These and other such compounds are widely used as drugs and therapeutic agents to treat cancer and a variety of other serious illnesses. See Coenzyme, Cyclic nucleotides, Nicotinamide adenine dinucleotide (NAD)

Nucleotides are generally classified as either ribonucleotides or deoxyribonucleotides. Both classes consist of a phosphorylated pentose sugar that is linked via an N-glycosidic bond to a purine or pyrimidine base. The combination of the pentose sugar and the purine or pyrimidine base without the phosphate moiety is called a nucleoside. See Purine, Pyrimidine

Ribonucleosides contain the sugar d -ribose, whereas deoxyribonucleosides contain the sugar 2-deoxyribose. The four most common ribonucleosides are adenosine, guanosine, cytidine, and uridine. The purine ribonucleosides, adenosine and guanosine, contain the nitrogenous bases adenine and guanine, respectively. The pyrimidine ribonucleosides, cytidine and uridine, contain the bases cytosine and uracil, respectively. Similarly, the most common deoxyribonucleosides include deoxyadenosine, deoxyguanosine, deoxycytidine, and thymidine, which contains the pyrimidine base thymine. Phosphorylation of the ribonucleosides or deoxyribonucleosides yields the corresponding ribonucleotide or deoxyribonucleotide. See Deoxyribonucleic acid (DNA), Enzyme, Nucleic acid, Ribonucleic acid (RNA)

nucleotide

[′nü·klē·ə‚tīd]
(biochemistry)
An ester of a nucleoside and phosphoric acid; the structural unit of a nucleic acid.
References in periodicals archive ?
Nucleotide sequence analyses indicated that the ferret HEV genome shares the highest nucleotide sequence identity (72.
In summary, by generating a large quantity of product from a small initial volume, PCR can simultaneously amplify small amounts of DNA and identify the target nucleotide sequences of interest.
Assuming that different nucleotide sequences of the gene (termed genotypes) indicate the presence of different species, then the number of genotypes is indicative of the number of species in the sample [ILLUSTRATION OMITTED].
Lengths and nucleotide sequences of the 5' and 3' noncoding regions of the 4 genes of SKA-1 were similar to those of the novel group of rotaviruses.
Today, all of GenBank's content is tightly integrated with two other databases, one (the EMBL Nucleotide Sequence Database) maintained by the European Molecular Biology Laboratory in Heidelberg, Germany, and the other (the DNA Data Bank of Japan) by the Center for Information Biology of the Japanese National Institute of Genetics in Mishima.
Prophylaxis can include surgical intervention, drug therapy, or the use of specific antisense nucleotide sequences to block the translation of the sense mRNA transcript called antisense RNA therapy.
1% nucleotide sequence identity) and the same 5 strains (TLS38 TLS42) appeared to be more divergent.
In the cell culture supernatant analysis by the RDV method, the specimen exhibited amplification of the partial nucleotide sequences of coxsackie A14 virus (nucleotide sequence data are available in the DDBJ/EMBL/GenBank databases under accession nos.
Nucleotide sequences of mitochondrial DNA extracted from the four Neandertal specimens resembled comparable genetic sequences previously taken from four other Neandertal fossils, the scientists report in the March Public Library of Science Biology.
Data types that can be merged using the Prophecy ToolKit include protein and nucleotide sequences, raw BLAST results, and other annotation conforming to Prophecy XML, such as Smith-Waterman results.
Nucleotide sequences were determined with the terminator cycle sequence kit (version 3.

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