Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone, the alternating sugar-phosphate structure composing the framework of a nucleic acid strand (Figure 3). Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds, or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Nitrogenous bases within DNA are categorized into the two-ringed purines adenine and guanine and the single-ringed pyrimidines cytosine and thymine. A nucleoside comprises the five-carbon sugar and nitrogenous base.įigure 2. The carbon atoms of the five-carbon deoxyribose are numbered 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ (1ʹ is read as “one prime”). The three components of a deoxyribonucleotide are a five-carbon sugar called deoxyribose, a phosphate group, and a nitrogenous base, a nitrogen-containing ring structure that is responsible for complementary base pairing between nucleic acid strands (Figure 1). Nucleotides that compose DNA are called deoxyribonucleotides. The building blocks of nucleic acids are nucleotides. In this section, we will discuss the basic structure and function of DNA.

In Mechanisms of Microbial Genetics, we will discuss in detail the ways in which DNA uses its own base sequence to direct its own synthesis, as well as the synthesis of RNA and proteins, which, in turn, gives rise to products with diverse structure and function. The base sequence of deoxyribonucleic acid (DNA) is responsible for carrying and retaining the hereditary information in a cell. Each nucleic acid strand contains certain nucleotides that appear in a certain order within the strand, called its base sequence. Like other macromolecules, nucleic acids are composed of monomers, called nucleotides, which are polymerized to form large strands.

In this chapter, we will discuss a fourth class of macromolecules: nucleic acids.

In Microbial Metabolism, we discussed three classes of macromolecules: proteins, lipids, and carbohydrates. Explain why the double helix of DNA is described as antiparallel.Identify the base pairs used in the synthesis of deoxyribonucleotides.Describe the biochemical structure of deoxyribonucleotides.

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