Chapter 3 - An introduction to gene function. Chapter 3 outlines the three activities of genes and provides some background information that will be useful in our deeper explorations in subsequent chapters. This chapter presents the following content: Storing information, replication, mutations. | Molecular Biology Fourth Edition Chapter 3 An Introduction to Gene Function Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Storing Information Producing a protein from DNA information involves both transcription and translation A codon is the 3 base sequence that determines what amino acid is used Template strand is the complementary DNA strand that is used to generate the mRNA Nontemplate strand is not used in RNA transcription 3- Protein Structure Proteins are chain-like polymers of small subunits, amino acids DNA has 4 different nucleotides Proteins have 20 different amino acids with: An amino group A hydroxyl group A hydrogen atom A specific side chain 3- Polypeptides Amino acids are joined together via peptide bonds Chains of amino acids are called polypeptides Proteins are composed of 1 or more polypeptides Polypeptides have polarity as does DNA Free amino group at one end | Molecular Biology Fourth Edition Chapter 3 An Introduction to Gene Function Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Storing Information Producing a protein from DNA information involves both transcription and translation A codon is the 3 base sequence that determines what amino acid is used Template strand is the complementary DNA strand that is used to generate the mRNA Nontemplate strand is not used in RNA transcription 3- Protein Structure Proteins are chain-like polymers of small subunits, amino acids DNA has 4 different nucleotides Proteins have 20 different amino acids with: An amino group A hydroxyl group A hydrogen atom A specific side chain 3- Polypeptides Amino acids are joined together via peptide bonds Chains of amino acids are called polypeptides Proteins are composed of 1 or more polypeptides Polypeptides have polarity as does DNA Free amino group at one end is the amino- or N-terminus Free hydroxyl group at the other end is the carboxyl- or C-terminus 3- Types of Protein Structure Linear order of amino acids is a protein’s primary structure Interaction of the amino acids’ amino and carboxyl groups gives rise to the secondary structure of a protein Secondary structure is the result of amino acid and carboxyl group hydrogen bonding among near neighbors Common types of secondary structure: a-helix b-sheet 3- Helical Secondary Structure In a-helix secondary structure polypeptide backbone groups H bond with each other Dashed lines in figure indicate hydrogen bonds between nearby amino acids 3- Sheet Secondary Structure The b-sheet pattern of 2° structure also occurs when polypeptide backbone groups form H bonds In the sheet configuration, extended polypeptide chains are packed side by side This side-by-side packing creates a sheet appearance 3- Tertiary Structure Total three-dimensional shape of a polypeptide is its tertiary .
