Components of Deoxyribonucleic Acid DNA

Complete hydrolysis of DNA gives phosphoric acid, a single sugar, and a mixture of four heterocyclic bases. The sugar is 2-deoxy-D-ribose. 

When we refer to these bases later, especially in connection with the genetic code, we will use the first letters of their names (capitalized) as abbreviations for their structures. 

N-glycosides have structures similar to those of 0-glycosides (Sec. 16.11). In 0-glycosides, the —OH group on the anomeric carbon is replaced by —OR in N-glycosides, that group is replaced by —NR2. 

A nucleoside is an N-glycoside a nitrogen atom of the heterocyclic base is connected to the anomeric carbon of the sugar. 

Because of their many polar groups, nucleosides are water soluble. Like other glycosides, they can be hydrolyzed readily by aqueous acid (or by enzymes) to the sugar and the heterocyclic base. For example. 

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FIGURE 7-1 Representative monosaccharides, (a) Two trioses, an aldose and a ketose. The carbonyl group in each is shaded, (b) Two common hexoses. (c) The pentose components of nucleic acids. D-Ribose is a component of ribonucleic acid (RNA), and 2-deoxy-o-ribose is a component of deoxyribonucleic acid (DNA). 

Replacement of a hydroxyl group by hydrogen yields a deoxy sugar. The derivative of ribose, deoxyribose, is a component of deoxyribonucleic acid (DNA). Similarly, deoxy derivatives of the two hexoses, galactose and mannose, occur as fucose and rhamnose, respectively, these being components of certain heteropolysaccharides. 

Resonance Raman Spectroscopy. If the excitation wavelength is chosen to correspond to an absorption maximum of the species being studied, a 10 —10 enhancement of the Raman scatter of the chromophore is observed. This effect is called resonance enhancement or resonance Raman (RR) spectroscopy. There are several mechanisms to explain this phenomenon, the most common of which is Franck-Condon enhancement. In this case, a band intensity is enhanced if some component of the vibrational motion is along one of the directions in which the molecule expands in the electronic excited state. The intensity is roughly proportional to the distortion of the molecule along this axis. RR spectroscopy has been an important biochemical tool, and it may have industrial uses in some areas of pigment chemistry. Two biological appHcations include the deterrnination of helix transitions of deoxyribonucleic acid (DNA) (18), and the elucidation of several peptide stmctures (19). A review of topics in this area has been pubHshed (20). 

Figure 9.12 Deoxy derivatives. These contain one less oxygen atom than the monosaccharide from which they are derived. 2-Deoxyribose is a most important deoxy pentose and is a major constituent of deoxyribonucleic acid (DNA). Deoxy hexoses are widely distributed among plants, animals and microorganisms especially as components of complex polysaccharides. Examples are rhamnose (6-deoxymannose), a component of bacterial cell walls, and fucose (6-deoxygalactose), which is often found in glycoproteins and is an important constituent of human blood group substances.

In deoxy sugars, one or more hydroxyl groups of the pyranose or furanose ring is substituted by hydrogen. A well-known example is 2-deoxyribose, which is a component of deoxyribonucleotides, the repeating units of deoxyribonucleic acids (DNA). Another example is L-fucose... 

In bacterial cells, nucleic acids are found in the form of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA carries the genetic blueprint for the cell and RNA acts as an intermediary molecule to convert the blueprint into proteins [8]. RNA has three forms namely, ribosomal, messenger and transfer RNAs. All the three types of RNA are essential for protein synthesis. Ribosomal RNA is the most abundant macromolecule, next to proteins, in an actively growing prokaryotic cell. It is a major component of the ribosome, the cellular machinery used to synthesize new proteins. There are three ribosomal RNA molecules in prokaryotes namely 5S (ca. 120 nucleotides), 16S (1500 nucleotides), and 23S (2900 nucleotides). 

The hypothesis of Stedman and Stedman (1951), which is supported by the more recent in vitro observations of Bonner and his colleagues [Huang and Bonner, 1962 Bonner and Huang, 1964 Bonner et al. 1968 (1)] and Allfrey (1966), postulates that another basic nuclear protein, histone, may modify or repress the genetic expression of deoxyribonucleic acid (DNA) in somatic cell nuclei. Thus it seems likely that the next study of biological interest based on a knowledge of the structures of the two components, DNA and protamine, will focus on the function and roles of the various components of a protamine in the sperm cell nuclei before, during, and after fertilization. 

Nucleic Acids. Phosphoms is an essential component of nucleic acids, polymers consisting of chains of nucleosides, a sugar plus a nitrogenous base, and joined by phosphate groups (43,44). In ribonucleic acid (RNA), the sugar is D-ribose in deoxyribonucleic acids (DNA), the sugar is 2-deoxy-D-ribose. 

The nucleus contains bundles of a fibrous material known as chromatin, which is made up of mixed proteins and deoxyribonucleic acid (DNA), the substance that carries the genetic information of the living organism of which the cell is a component. All cells replicate by division. When a cell replicates, DNA in the chromatin of the nucleus passes the genetic information from one generation to the next one. As the cell divides, the chromatin clusters into rodlike structures known as chromo-... 

The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which carry embedded in their complex molecules the genetic information that characterizes every organism, are found in virtually all living cells. Their molecules are very large and complex biopolymers made up basically of monomeric units known as nucleotides. Thus DNA and RNA are said to be polynucleotides. The nucleotides are made up of three bonded (linked) components a sugar, a nitrogenous base, and one or more phosphate groups ... 

The neuron contains severai speciaiized components, caiied organeiies, which are anaiogous to the organs of a body. The nucleus is approximateiy 3-18 pm in diameter and contains deoxyribonucleic acid (DNA). The nuciear membrane has pores to aiiow passage of substances in and out of the nucieus. The nucieus aiso has a body within caiied the nucieoius, which manufactures ribosomes and contains ribonucieic acid (RNA), a coating of DNA, and severai enzymes. 

Three major components in the transmission of genetic information are deoxyribonucleic acids (DNA), ribonucleic acids (RNA), and proteins. The genetic code expressed through DNA ultimately determines which proteins a cell will produce. Coiled and supercoiled DNA molecules contain numerous sequences of nucleotides that may be transcribed as RNAs and translated to many different proteins. DNA molecules also contain long sequences of nucleotides not coding for protein and whose purpose is not completely understood. A gene is a specific sequence of DNA that encodes a sequence of messenger... 

The nucleic acids play a central role in the storage and expression of genetic information (see p. 236). They are divided into two major classes deoxyribonucleic acid (DNA) functions solely in information storage, while ribonucleic acids (RNAs) are involved in most steps of gene expression and protein biosynthesis. All nucleic acids are made up from nucleotide components, which in turn consist of a base, a sugar, and a phosphate residue. DNA and RNA differ from one another in the type of the sugar and in one of the bases that they contain. 

Polynucleotides consisting of ribonucleotide components are called ribonucleic acid (RNA), while those consisting of deoxyribonu-cleotide monomers are called deoxyribonucleic acid (DNA see p. 84). To describe the structure of polynucleotides, the abbreviations for the nucleoside components are written from left to right in the 5 - 3 direction. The position of the phosphate residue is also sometimes indicated by a p . In this way, the structure of the RNA segment shown Fig. 2 can be abbreviated as. .pUpG.. or simply as... 

Nucleotides have a variety of roles in cellular metabolism. They are the energy currency in metabolic transactions, the essential chemical links in the response of cells to hormones and other extracellular stimuli, and the structural components of an array of enzyme cofactors and metabolic intermediates. And, last but certainly not least, they are the constituents of nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (ENA), the molecular repositories of genetic information. The structure of every protein, and ultimately of every biomolecule and cellular component, is a product of information programmed into the nucleotide sequence of a cell s nucleic acids. The ability to store and transmit genetic information from one generation to the next is a fundamental condition for life. 

A typical molecular analysis of various micro-organisms is shown in Table 5.9U ) Most of the elemental composition of cells is found in three basic types of materials—proteins, nucleic acids and lipids. In Table 5.10, the molecular composi-tion of a bacterium is shown in more detail. Water is the major component of the cell and accounts for 80-90 per cent of the total weight, whilst proteins form the next most abundant group of materials and these have both structural and functional properties. Most of the protein present will be in the form of enzymes. Nucleic acids are found in various forms—ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Their primary function is the storage, transmission and... 

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