Lecture 18 - DNA Structure and History PDF

Lecture 18 – DNA Structure and History  Day 1 – The Cell Nucleus Cytoplasm (all the other stuff…) Membrane (and/or Cell Wall)  Unit 1 – Bu...

Lecture 18 – DNA Structure and History  Day 1 – The Cell Nucleus Cytoplasm (all the other stuff…) Membrane (and/or Cell Wall)  Unit 1 – Building Blocks Transport Macromolecules Membrane (and/or Cell Wall) Image made with BioRender  Unit 2 – Catabolism + Anabolism Respiration Catabolism (e.g. glycolysis) Anabolism (e.g. photosynthesis) Image made with BioRender  Every single arrow in metabolic pathways is a reaction catalyzed by a unique protein! That’s a LOT of proteins!!! How does a cell make proteins? Complete Metabolism Map KEGG Pathway  Exam 3 – Genetic Information Flow (The Central Dogma of Biology) DNA RNA Protein Image made with BioRender  Central Dogma of Biology Central dogma: describes how genetic information provides instructions for cells  Nucleotides Nucleotide: Monomer composed of: Nitrogenous base Pentose sugar Phosphate  Nitrogenous bases Thymine (T) Adenine (A) Uracil (U) (RNA only) Guanine (G) Cytosine (C) Structure of DNA  Heredity Predates discovery of DNA and field of genetics as we know it Heredity: inheritance of traits from parents to offspring  Heredity Predates discovery of DNA and field of genetics as we know it Heredity: inheritance of traits from parents to offspring Big Question: How are traits determined?  Race to discover genetics Hundreds of scientists contributed to discovery of DNA. Here are a few and their milestones: Frederick Griffith (1928): Transforming principle Avery, MacLeod, McCarty (1944): DNA = transforming principle Hershey-Chase (1952): DNA = genetic material Rosalind Franklin (1952): First structure of DNA Watson & Crick (1953): Finalized structure of DNA Frederick Griffith (1877-1941) Bacteriologist studying vaccines against pneumonia (Streptococcus pneumoniae) Two strains of S. pneumoniae: S: Smooth colony—virulent and deadly R: Rough colony—nonvirulent to mice Discovered inheritance of virulence by his experiments The “transformation principle”  Griffith transformation experiment (1928) OpenStax Biology 2e  Avery, McCarty, and McLeod Experiment (1944) Oswald Avery Maclyn McCarty Colin McLeod Repeated Griffith experiment, but washed away or destroyed different combinations of cellular components Determined that only DNA caused transformation of S. pneumoniae Cautious conclusions—feared possible contamination Avery, McCarty, and McLeod Experiment (1944)  Hershey-Chase Experiment (1952) Bacteriophage Bacteria Image from Eye of Science / Science Source Martha Chase & Alfred Hershey Bacteriophage Bacteriophage: virus that infects bacteria Phage components: Protein (coat/shell) DNA (core) Which one is the genetic material?  Hersey-Chase Experiment (1952) 1. DNA (32P) and Protein (35S) were radioactively labelled in phage 2. Bacteria infected by different radioactive phages 3. Only radioactive DNA (32P) found inside bacteria DNA = genetic material! OpenStax Biology 2e  The Structure of DNA 3 papers simultaneously published in the same issue of Nature in 1953: Watson & Crick: A Structure for Deoxyribose Nucleic Acid Wilkins, Stokes, & Wilson: Molecular Structure of Deoxypentose Nucleic Acids Franklin & Gosling: Molecular Configuration in Sodium Thymonucleate Watson and Crick used Rosalind Franklin’s x-ray image of DNA to construct the double helix of DNA Watson & Crick solved structure first and are credited with “winning” the race to discover the structure of DNA  Video Activity The Double Helix Watch “The Double Helix” video and complete the activity alongside it (Participation). We will review it together at the end of class.