Sugars in DNA

The sugar component in RNA is ribose, and the sugar in DNA is 2 -deoxy-ribose. (The prefix 2 -deoxv indicates that oxygen is missing from the 2 position of ribose.) DNA contains four different amine bases, two substituted purines (adenine and guanine) and two substituted pyrimidines (cytosine and thymine). Adenine, guanine, and cytosine also occur in RNA, but thymine is replaced in RNA by a closely related pyrimidine base called uracil. 

Since the sugar in DNA is deoxyribose, the polynucleotide that makes up DNA can be written as... 

The two forms of mirror images are called enantiomers, or stereoisomers. All amino acids in proteins are left-handed, and all sugars in DNA and RNA are right-handed. Drug molecules with chiral centers when synthesized without special separation steps in the reaction process result in 50/50 mixtures of both the left- and right-handed forms. The mixture is often referred to as a racemic mixture. 

All nucleic acids consist of covalently linked nucleotides. Each nucleotide has three characteristic components (1) a purine or pyrimidine base (2) a pentose and (3) a phosphate group. The purine or pyrimidine bases are linked to the C-T carbon of a deoxyribose sugar in DNA or a ribose sugar in RNA. The phosphate groups are linked to the sugar at the C-5 and C-3 positions. The purine bases in both DNA and RNA are always adenine (A) and guanine (G). The pyrimidine bases in DNA are thymine (T) and cyto-... 

The sugar component in RNA is ribose, and the sugar in DNA is 2-deoxyribose (2-deoxy means that oxygen is missing from C2 of ribose). 

Deoxyribose 2-Deoxyribose is an aldopentose that is the structural sugar in DNA. This sugar is called deoxy because it does not have a hydroxyl group on carbon 2. Deoxyribose cyclizes into a furanose (five-membered) ring system. The structures of D-2-deoxyribose and (3-D-2-deoxyribofuranose are given in Figure 12.55. 

Nucleosides A nucleoside is a pyrimidine or purine base covalently bonded to a sugar. In DNA, the sugar is deoxyribose and so this is a deoxynucleoside. There are four types of deoxynucleoside in DNA deoxyadenosine, deoxyguanosine, deoxythymidine and deoxycytidine. 

All our descriptions of ribonucleosides, ribonucleotides, and ribonucleic acid also apply to the components of DNA. The principal difference between RNA and DNA is the presence of D-2-deoxyribose as the sugar in DNA instead of the D-ribose found in RNA. The prefix deoxy- means that an oxygen atom is missing, and the number 2 means it is missing from C2. 

Adhikary A, Kumar A, Sevilla MD. (2006) Photo-induced hole transfer from base to sugar in DNA Relationship to primary radiation damage. Radiation Res 165 479-484. 

The five-carbon sugar in RNA is ribose, and the sugar in DNA is 2 -deox)Tribose. The only difference between these two sugars is the absence of an hydroxyl group on the 2 carbon of 2 -deoxyribose. The purines in both DNA and RNA are adenine and guanine. Both DNA and RNA contain the pyrimidine cytosine however, the fourth base is thymine in DNA and uracil in RNA. The chemical compositions of DNA and RNA are summarized in Table 24.1. 

All nncleic acids are polynucleotides, with each nucleotide being made np of a base, a sugar unit, and a phosphate. The composition of DNA differs from that of RNA in two major ways (see Figure 1). Whereas DNA contains the bases gnanine (G), cytosine (C), adenine (A), and thymine (T), RNA contains G, C, and A, but it contains uracil (U) in place of thymine. Both DNA and RNA contain a five-membered cyclic sngar (a pentose). RNA contains a ribose sngar. The sugar in DNA, however, is 2 -deoxyribose. 

Fig. 3-27 The sugar in DNA is 2-deoxy-D-ribose (2-deoxy-P-D-ribofuranose ieft) in RNA it is o-ribose (P-D-ribofuranose right), it is the -anomer in each case that is present in the nucleic acid.

Examples of current usage of the absolute notation based on glyceraldehyde are D-( + )-glucose for blood-sugar, D-(-)-fructose for fruit sugar and D-(- )-deoxyribose for the sugar in DNA. 

The D/R sugar piece of the nucleic acid puzzle is seen in space as glyceraldehyde, which is half the size of the ribose sugar in DNA. Glyceraldehyde is a reactive molecule that your body puts together to form other larger sugars with a few steps. 

It should be stressed at this point that, although J s of a conformationally equilibrating species usually represent population-weighted time averages, the number of observables readily exceeds the number of parameters to be determined, so that both reliable population distributions as well as geometrical information can be extracted from J data. For a brief review of results of Jhh analysis of sugars in DNA sequences, see e.g. [87A1]. 

The chemical building blocks for nucleic acids (DNA and RNA) are nucleotides covalently assembled together by 3, S -phosphodiester bonds between adjacent pentose moieties. a2-deoxy-D-ribose is the sugar in DNA and a-D-ribose is the sugar in RNA (see Fig. 2). The 1 -carbon atom of the pentose is linked to one of four nitrogen containing heterocyclic bases adenine (A) or guanine (G), two purines cytosine (C) or thymine (T), two pyrimidines. In RNA uracil (U) replaces thymine. No particular periodicity characterizes the succession of the nucleotides. 

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