2.4 Physical chemistry of nucleic acids A Variety of DNA Structures A Variety of DNA Structures A form A form Separating the Two Strands of a DNA Double Helix Separating the Two Strands of a DNA Double Helix Reuniting the Separated DNA Strands Reuniting the Separated DNA Strands Hybridization of Two Different Polynucleotide Chains Hybridization of Two Different Polynucleotide Chains DNAs of Various Sizes and Shapes DNAs of Various Sizes and Shapes The Relationship between DNA Size and Genetic Capacity The Relationship between DNA Size and Genetic Capacity DNA Content and the C-Value Paradox DNA Content and the C-Value Paradox

Nucleic acid can form several types of double helix B-DNA A-DNA Z-DNA Bp/turn Rotation/bp +34.6º +34.7º -30.0º Vertical rise/bp 3.38Å 2.56 Å 5.71Å Helical diameiter 19 Å 23Å 18Å A variety of DNA structure

Separating the two strands of a DNA double helix DNA denature; DNA melting; T m (The temperature at which the DNA strands are half denatured.) Hyperchromic shift

Reuniting the separated DNA strands Annealing / renaturation Three important factors: Temperature : ~T m -25°C DNA concentration : the higher the concentration, the faster the annealing Renaturation time: The longer the time,the more will occur. C 0 t: DNA concentration and time

The more complex a DNA, the higher its C 0 t 1/2

DNA/RNA hybridization

DNAs of Various sizes and shapes The sizes are expressed three ways: molecular weight, number of base pairs and length. 1 helical turn = 10.5 bp = 34Å; 1bp = 660 d. Measure DNA sizes electron microscope gel electrophoresis

Chapter 3 An Introduction to Gene Function

Color-enhanced scanning electron micrograph of DNA strands showing transcription detail

Three major activities of gene Information Information Replication Replication Mutation Mutation

3.1 Storing Information  Overview of Gene Expression  Protein Structure  Protein Function The Relationship between Genes and Proteins  Discovery of Messenger RNA  Transcription  Translation Ribosomes: Protein-Synthesizing Machines Transfer RNA: The Adapter Molecule Initiation of Protein Synthesis Translation Elongation Termination of Translation and mRNA Structure

3.1 Storing Information  Overview of Gene Expression  Protein Structure  Protein Function The Relationship between Genes and Proteins The Relationship between Genes and Proteins  Discovery of Messenger RNA  Transcription  Translation Ribosomes: Protein-Synthesizing Machines Ribosomes: Protein-Synthesizing Machines Transfer RNA: The Adapter Molecule Transfer RNA: The Adapter Molecule Initiation of Protein Synthesis Initiation of Protein Synthesis Translation Elongation Translation Elongation Termination of Translation and mRNA Structure Termination of Translation and mRNA Structure

Tertiary structure of myoglobin

Tertiary structure of the core region common to all protein kinase

The globular domains of an immunoglobin

Evidence for One gene-one enzyme

Pathway of pantothenate synthesis

3.2 Replication Semi-conservative replication

3.3 Mutations Sickle-Cell Disease