In order to study the structure of nucleic acid, it is essential to study the structure of its monomer. This unit joins to a third nucleotide, and the process is repeated to produce a long nucleic acid chain (Figure \(\PageIndex{1}\)). Purines have a double ring structure, and pyrimidines have a single ring. nucleic acids are the genetic material, and then exploring the chemical structure of nucleic acids. Nucleic acids are large polymers formed by linking nucleotides together and are found in every cell. In DNA double helix, the two strands of DNA are held together by hydrogen bonds.The nucleotides on one strand base pairs with the nucleotide on the other strand. Each nucleotide is made up of three parts: a nitrogen-containing ring structure called a nitrogenous base, a five-carbon sugar, and at least one phosphate group. … This was extended to large RNA molecules, and the structure … The sequence of nucleotides in the DNA segment shown in Figure \(\PageIndex{1}\) would be written 5′-dG-dT-dA-dC-3′, which is often further abbreviated to dGTAC or just GTAC. For the two strands of the double helix to fit neatly, a pyrimidine must always be paired with a purine. Moreover, as their model showed, the two chains are twisted to form a double helix—a structure that can be compared to a spiral staircase, with the phosphate and sugar groups (the backbone of the nucleic acid polymer) representing the outside edges of the staircase. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. STRUCTURE OF DNA Dr. N. Sivaranjani, MD Asst. This is why these compounds are known as nucleic acids. Nucleic acids consist of a sugar (pentose), nitrogenous bases (purines and pyrimidines), and phosphoric acid. In 1953, Watson and Crick described the structure of DNA. It can be represented as a list of bases which are paired in a nucleic acid … Why is it structurally important that a purine base always pair with a pyrimidine base in the DNA double helix? The entire genetic content of a cell is known as its genome, and the study of genomes is genomics. RNA is usually single-stranded and is made of ribonucleotides that are linked by phosphodiester bonds. 2 Nucleic acids:structure and function The monomers, called nucleotides, that make up these macromolecules are composed of a five-membered carbohydrate ring (furanose), a nitrogen-containing base, and a phosphate group. circle the atoms that comprise the backbone of the nucleic acid chain. In this section, we will examine the structures of DNA and RNA, and how these structures are related to the functions these molecules perform. Unlike proteins, which have 20 different kinds of amino acids, there are only 4 different kinds of nucleotides in nucleic acids. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Cytosine, thymine, and uracil are classified as pyrimidines which have a single carbon-nitrogen ring as their primary structure (Figure 1). They are bases because they contain an amino group that has the potential of binding an extra hydrogen, and thus, decreases the hydrogen ion concentration in its environment, making it more basic. The structures of purine and pyrimidine bases and their corresponding nucleosides and nucleotides are shown in Fig. DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. There are two types of nucleic acid: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). If a cell requires a certain protein to be synthesized, the gene for this product is turned “on” and the messenger RNA is synthesized in the nucleus. This intermediary is the messenger RNA (mRNA). Missed the LibreFest? The knowledge that 24-year-old Miescher derived from studying the pus on dirty hospital bandages led to the discovery and analysis of nucleic acid. This will cause the DNA to bulge. New copies of DNA are created by the process of DNA replication. Nucleotides of Nucleic Acids DNA is composed of two sugar-phosphate backbones and nucleotide bases. nucleic acids are the genetic material, and then exploring the chemical structure of nucleic acids. In the nucleus, nucleotide monomers are linked together comprising of distinct components namely a Phosphate Group, Nitrogenous Bases or Ribose and Deoxyribose. In biological systems, they serve as information-carrying molecules or, in … In a double stranded DNA molecule, the two strands run antiparallel to one another so that one strand runs 5′ to 3′ and the other 3′ to 5′. Figure 1. Chargaff drew no conclusions from his work, but others soon did. It can mean something … DNA and RNA are made up of monomers known as nucleotides. These sugars form a bond with the phosphate groups also present in nucleotides. deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Chemically speaking, DNA and RNA are very similar. Nucleic acids are polynucleotide chains in which ribonucleotides and deoxyribonucleotides are the monomeric units (Section 1.4) of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) respectively.Nucleotides are composed of three component parts: a heterocyclic ring structure, a pentose sugar and a phosphate group, each of which contributes to the chemistry of the unit. For amino acid sequences in proteins, the convention is to write the amino acids in order starting with the N-terminal amino acid. Bases can be divided into two categories: purines and pyrimidines. Deoxyribonucleic acid (DNA) The nucleic acid that stores genetic information. Antiparallel structure of DNA strands. Controlling the structure and activity of nucleic acids dramatically expands their potential for application in therapeutics, biosensing, nanotechnology, and biocomputing. Adenine and guanine are classified as purines. The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. 2. The basic structure of nucleic acids is Nitrogenous bases, the Sugar moiety, and the Phosphate molecule. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Nucleic Acid Structure Because nucleic acids can form huge polymers which can take on many shapes, there are several ways to discuss the “structure of nucleic acid”. This is known as the base complementary rule. Basic structure Nucleic acids are polynucleotides—that is, long chainlike molecules composed of a series of nearly identical building blocks called nucleotides. Describe the basic structure of nucleic acids Nucleic acids are the most important macromolecules for the continuity of life. DNA repair enzymes may recognize the bulge and replace the incorrect nucleotide. This means A can pair with T, and G can pair with C, as shown in Figure 3. Nucleic acids include ribonucleic acid, or RNA, and deoxyribonucleic acid, or DNA. Each nucleotide, in turn, is composed of three distinct elements: a five-carbon ribose sugar, a phosphate group and a nitrogenous base. A mutation occurs, and cytosine is replaced with adenine. i.e a pentose. This opened the era of single-crystal analyses of nucleic acid structures in which increasingly larger oligonucleotides were crystallized and their three-dimensional structure solved. Nucleotides consist of a nucleoside (the combination of a pentose monosaccharide molecule and a … In a pseudoknot, the knotted region the "()" pairing cannot exceed 9 or 10 basepairs. The base is attached to the 1′ position of the ribose, and the phosphate is attached to the 5′ position. The secondary structure is responsible for the shape that the nucleic acid assumes. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. 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