28: Biomolecules - Nucleic Acids
- Page ID
- 448867
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)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.
- 28.0: Why This Chapter?
- This chapter introduces nucleic acids, focusing on their essential roles in genetic information storage and transmission. It discusses the structures and functions of DNA and RNA, highlighting their involvement in heredity, protein synthesis, and cellular activities. The chapter emphasizes the importance of understanding nucleic acids for grasping molecular biology concepts and the mechanisms underlying life processes.
- 28.1: Nucleotides and Nucleic Acids
- This section covers the structure and functions of nucleotides and nucleic acids. Nucleotides, composed of a sugar, phosphate group, and nitrogenous base, are the building blocks of nucleic acids (DNA and RNA). The chapter discusses how nucleotides link to form nucleic acids, the differences between DNA and RNA, and the roles these biomolecules play in genetic information storage and transmission. Understanding nucleotides is crucial for comprehending cellular processes and molecular biology.
- 28.2: Base Pairing in DNA
- The section discusses the significance of base pairing in DNA, emphasizing how specific pairs of nitrogenous bases—adenine with thymine and cytosine with guanine—form hydrogen bonds. This complementary base pairing is crucial for the double-helix structure of DNA and ensures accurate replication and transcription during cellular processes. The precise pairing mechanism contributes to the stability of the DNA molecule and plays a vital role in genetic coding and expression.
- 28.3: Replication of DNA
- The section covers the process of DNA replication, detailing how the double helix unwinds and each strand serves as a template for synthesizing new complementary strands. Key enzymes, such as helicase, polymerase, and ligase, play vital roles in the replication process. The accuracy of base pairing ensures that the genetic information is preserved and passed on to daughter cells, maintaining the integrity of the genetic code.
- 28.4: Transcription of DNA
- Transcription is the process by which DNA is converted into RNA. It begins when RNA polymerase binds to the promoter region of a gene, unwinding the DNA strands. The enzyme synthesizes a complementary RNA strand by adding ribonucleotides, following base-pairing rules. After synthesis, the mRNA undergoes processing, including the addition of a 5' cap and a poly-A tail, before it exits the nucleus to be translated into protein. This mechanism is vital for gene expression and cellular function.
- 28.5: Translation of RNA - Protein Biosynthesis
- Translation is the process of synthesizing proteins from mRNA. It occurs in three main stages: initiation, elongation, and termination. Ribosomes read the mRNA sequence in codons, which correspond to specific amino acids. tRNA molecules, carrying amino acids, bind to the ribosome at the anticodon region, facilitating the assembly of a polypeptide chain. Once a stop codon is reached, the newly formed protein is released. This process is crucial for cellular functions and organismal developement.
- 28.6: DNA Sequencing
- DNA sequencing involves determining the order of nucleotides in DNA. Key methods include Sanger sequencing, which uses chain-terminating nucleotides for small-scale projects, and next-generation sequencing (NGS), which enables rapid and extensive sequencing of entire genomes and has revolutionized genomics, allowing for advancements in medical research, personalized medicine, and evolutionary studies. These techniques provide insights into genetic variation and the role of genes in health.
- 28.7: DNA Synthesis
- DNA synthesis involves creating new DNA strands, primarily through replication or artificial methods. DNA polymerase plays a crucial role by adding nucleotides complementary to a template strand while ensuring fidelity through proofreading. Techniques such as solid-phase synthesis and PCR are key in labs, enabling advances in gene therapy and synthetic biology. These methods facilitate the manipulation and study of genetic material.
- 28.8: The Polymerase Chain Reaction
- The Polymerase Chain Reaction (PCR) is a powerful technique used to amplify specific DNA sequences, making millions of copies from a small sample. It involves repeated cycles of denaturation, annealing of primers, and extension by DNA polymerase. PCR is crucial in various applications, including genetic research, forensics, and medical diagnostics, allowing scientists to analyze DNA quickly and accurately.
- 28.9: Chemistry Matters—DNA Fingerprinting
- DNA fingerprinting, or profiling, is a technique used to identify individuals based on unique patterns in their DNA. This method analyzes variable regions of DNA, particularly short tandem repeats (STRs), which differ significantly among individuals. It's widely utilized in forensic science for crime scene investigations, paternity testing, and identifying genetic relationships. DNA fingerprinting's reliability stems from its ability to distinguish between closely related individuals.
- 28.11: Summary
- This summary outlines the key aspects of nucleic acids, including the structure and function of DNA and RNA, the processes of transcription and translation, and the significance of DNA replication. It emphasizes the role of nucleic acids in genetic information storage, expression, and heredity. The chapter also covers techniques like DNA sequencing and polymerase chain reaction (PCR), which have crucial applications in biotechnology and medicine.