Nucleotides nomenclature, Table

Nitrogenous base plus sugar moiety are called nucleosides. Ribonucleic acids (RNA) resemble DNA in that nucleoside monophosphates are joined through phosphodiester bonds. RNAs differ in that the sugars are p-D-ribose units and the pyrimidine uracil is found in place of thymine. Molecular structures and nomenclature for nitrogenous bases, nucleosides, and nucleotides are delineated in Table 2.2. 

The nomenclature for the commonly found bases, nucleosides, and nucleotides is shown in Tables I-l-2a and -2b. Note that the deoxy part of the names deoxythymidine, dTMP, etc., is sometimes understood, and not expressly stated, because thymine is almost always found attached to deoxyribose. 

Table 20.1 Classification and nomenclature of bases, nucleosides and nucleotides...

Both DNA and RNA contain two major purine bases, adenine (A) and guanine (G), and two major pyrimidines. In both DNA and RNA one of the pyrimidines is cytosine (C), but the second major pyrimidine is not the same in both it is thymine (T) in DNA and uracil (U) in RNA Only rarely does thymine occur in RNA or uracil in DNA The structures of the five major bases are shown in Figure 8-2, and the nomenclature of their corresponding nucleotides and nucleosides is summarized in Table 8-1. 

Table 10 The Nucleic Bases, Their Proton Ionization Constants (pit,), and the Nomenclature of Their Nucleoside and Nucleotide Derivatives...

Structure of the nucleotide in DNA and RNA. The base adenine is used as an example. See Table 27-1 for a complete nomenclature of nucleosides and nucleotides. 

Table 27-1 gives the nomenclature of purine and pyrimidine nucleosides and nucleotides. Names of purine nucleosides end in -osine, whereas those of pyrimidine nucleosides end in -idine guanine nucleoside is guanosine and should not be confused with guanidine, which is not a nucleic acid base thymidine is a deoxyriboside. 

The nomenclature of nucleotides and their constituent units was presented in Chapter 4. Recall that a nucleoside is a purine or pyrimidine base linked to a sugar and that a nucleotide is a phosphate ester of a nucleoside. The names of the major bases of RNA and DNA, and of their nucleoside and nucleotide derivatives, are given in Table 25.1. 

The nomenclature of the HLA system is determined by the World Health Organization (WHO) Nomenclature Committee and reflects both the serological and the nucleotide levels of classification. The 1991 report of the Nomenclature Committee listed 27 HLA-A specificities, 59 HLA-B specificities, and 10 HLA-C specificities as shown in Table 1 (B17). These are the specificities that are detectable at the serological level. Contributing to some of these individual specificities, however, can be a large number of different alleles. At least 10 different alleles code for the specificity HLA-A2, for example, and 7 code for HLA-B27. To accommodate this complexity, the Nomenclature Committee has... 

Table 8.4 lists some of the allelic variants that are found among human CYP genes and includes the nomenclature and the actual nucleotide amino acid substitutions, the resultant abnormal phenotype, and an example of the clinical consequence. 

The enzymatic roles of the folate coenzymes were first studied in connection with purine nucleotide biosynthesis, although some of the major manifestations of folate deficiency are due to impairment of thymidylate and DNA synthesis. Figure 5-1 shows the structure of folic acid and identifies its component parts. Nomenclature in this area has changed frequently and is sometimes confusing and inconsistent Table 5-1 gives the latest approved nomenclature, together with alternatives also found in the literature. The field of folic acid biochemistry is discussed in depth by Blakley (2). 

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