DNADiscovery that DNA, not Protein is Genetic Material Fredrick Griffith Oswald Avery Hershey and Chase Erwin Chargaff Rosalind Franklin Watson and CrickDNA Structure Nucleotides Nitrogen Bases Base-Pairing RuleDNA Replication Helicase DNA Polymerase Result
Unit IV Learning Goal 3 DESCRIBE THE STRUCTURE OF DNA, ITSDISCOVERY, AND ITS IMPORTANCE IN DNA REPLICATION.
Discovery that DNA not Protein is Genetic MaterialFrederick Griffith(1928) Heat killed pneumonia bacteria could transform harmless bacteria into bacteria that caused pneumonia.
Avery’s World Pneumonia leading cause of death in America, early 1900’s. 50,000 deaths/year. During World War I called the “Captain of Death” in hospitals. http://www.nlm.nih.gov/ http://www.who.int/mediacentre/factsheets/fs331/en/index.html
Oswald Avery (1944)Discovered that nucleicacids were the onlymolecules that couldtransform bacteria. DNA not RNA was responsible for transformation because it still occurred when enzymes had destroyed the RNA.
Hershey and Chase(1952) Found viruses that attack bacteria did so by injecting their DNA not proteins.
Discovery of DNA StructureErwin Chargaff(1949) Found that the DNA molecule was double- stranded. Adenine = Thymine Guanine = Cytosine
Rosalind Franklin Discovered that the DNA molecule is a helix (twisted) through X-ray diffraction research.
James Watson andFrancis Crick Used the research of the others to figure out the exact structure of the DNA molecule.
DNA Structure Nucleotides – DNA is made up of nucleotides. Each nucleotide consists of deoxyribose sugar, phosphate, and one of four nitrogen bases. Nitrogen Bases – The nitrogen bases are, adenine, thymine, guanine, and cytosine. Base Pairing Rule – Nitrogen bases are bonded with hydrogen bonds according to the base-pairing rule: A – T and G - C
DNA Replication Helicase The enzyme helicase causes the DNA double helix to unwind and unzip down the middle. DNA Polymerase Loose nucleotides are then bonded to exposed nitrogen bases on both sides of the molecule by another enzyme called DNA polymerase. Result At the end of the process there are two copies of the original DNA molecule. This is called semiconservative replication because one strand of the original molecule is contained in each new molecule.
Pneumonia Today World Health Organization calls Pneumonia “ The Forgotten Killer of Children” http://whqlibdoc.who.int/publications/2006/9280640489_eng.pdf