28: Nucleic Acids
When you have completed Chapter 28, you should be able to
- fulfill all of the detailed objectives listed under each individual section.
- draw the structure of a given nucleotide.
- discuss the structure of DNA and RNA.
- describe the processes involved in DNA replication, transcription, translation, and protein synthesis.
- define, and use in context, the key terms introduced in this chapter.
Two types of nucleic acids are found in cells—deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). These highly complex substances are built up from a number of simpler units, called nucleotides. Each nucleotide consists of three parts: a phosphoric acid residue, a sugar and a nitrogen‑containing heterocyclic base. Thus, in order to understand the biochemistry of the nucleic acids, you must first study the chemistry of the sugars (see Chapter 25) and simple heterocyclic systems. We have already discussed certain aspects of the structure of heterocyclic ring systems during our study of aromaticity (Sections 15.5–15.6). You may find it helpful to review this chapter.
Chapter 28 examines the structure and replication of DNA and then describes the structure and synthesis of RNA. The chapter closes with a brief study of the role played by RNA in the biosynthesis of proteins.
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- 28.0: Chapter Objectives
- Nucleic acids are indispensable molecules that underpin the central dogma of molecular biology, governing the storage, transmission, and expression of genetic information in all living organisms. Understanding their structure, function, and interactions is fundamental to unraveling the complexities of life and advancing fields such as medicine, biotechnology, and genetics.
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- 28.4: Transcription of DNA
- Three types of RNA are formed during transcription: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). These three types of RNA differ in function, size, and percentage of the total cell RNA. mRNA makes up only a small percent of the total amount of RNA within the cell, primarily because each molecule of mRNA exists for a relatively short time; it is continuously being degraded and resynthesized.