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Chapter 12-13 – DNA and How Genes Work Avery, MacLeod and McCarty • What is transforming agent? DNA or protein? Avery, MacLeod and McCarty Avery, MacLeod and McCarty conclusion • DNA carries the heritable information 1944 Hershey and Chase Martha Cowles Chase Alfred Day Hershey Hershey and Chase Bacteriophage: viruses that infect bacterial cells Hershey and Chase Hershey and Chase conclusion • Genetic material in virus was DNA • DNA is agent of heredity INDEPENDENT FUNCTIONS OF VIRAL PROTEIN AND NUCLEIC ACID IN GROWTH OF BACTERIOPHAGE* B~ A. D. HERSHEY AND MARTHA CHASE (From the Department of Genetics, Carnegie Institution of Washington, Cold Spring Harbor, Long Island) (Received for publication, April 9, 1952) The work of Doermaml (1948), Doermann and Dissosway (1949), and Anderson and Doermann (1952) has shown that bacteriophages T2, T3, and T4 multiply in the bacterial cell in a non-infective form. The same is true of the phage carried by certain lysogenic bacteria (Lwoff and Gutmann, 1950). Little else is known about the vegetative phase of these viruses. The experiments reported in this paper show that one of the first steps in the growth of T2 is the release from its protein coat of the nucleic acid of the virus particle, after which the bulk of the sulfur-containing protein has no further function. DNA – just what is it? Nucleic Acids Monomers = nucleotides Polymer = DNA, RNA DNA Nucleotide (monomer) 4 bases DNA “double helix” DNA A-T G-C DNA “double helix” A-T G-C Rosalind Franklin (1920-1958) X-ray crystalography Structure of DNA Watson and Crick 1953 Watson and Crick (1953) DNA Replication Expression DNA Replication DNA Replication DNA Replication DNA Replication DNA Replication DNA Replication DNA Information stored in order of the bases +/- 1200 copies Central Dogma of Cell Biology DNA (gene) Protein One-Gene/One-Polypeptide Hypothesis Each gene codes for a specific and unique protein 1958 – Nobel Prize GENETICS: TA TUM AND BEADLE GENETIC CONTROL OF BIOCHEMICAL REACTIONS IN NEUROSPORA: AN "AMINOBENZOICLESS" MUTANT* By E. L. TATUM AND G. W. BEADLE DEPARTMENT OF BIOLOGY, STANFORD UNIVERSITY Communicated April 17, 1942 Para-aminobenzoic acid has recently been recognized as a factor required for the growth of a number of micro6rganisms' and as a member of the vitamin B group.2 One of the number of x-ray induced mutants of Neurospora crassa, obtained as described elsewhere,' is characterized by the loss of ability to synthesize p-aminobenzoic acid. This "aminobenzoicless“ mutant is differentiated from normal by a single gene, is unable to grow on unsupplemented synthetic medium, but its growth is indistinguishable from normal when p-aminobenzoic acid is supplied. Central dogma of molecular biology Extracting and using the information Two Steps: 1. 2. Extracting and using the information The information Extracting and using the information An intermediate Extracting and using the information The product Translation – constructing a protein DNA mRNA protein Transcription DNA copied into mRNA mRNA single-stranded U instead of T Translation – constructing a protein DNA mRNA protein Instructions are coded in the order of the bases Instructions are an ordered list of amino acids in protein 20 amino acids Protein is a polymer of amino acids Each ‘word’ in the DNA-RNA vocabulary is 3 ‘letters’ long One “word” Each ‘word’ in the DNA-RNA vocabulary is 3 ‘letters’ long A ‘word’ is called a codon Triplet Codon: group of 3 bases that specifies an amino acid The Genetic Code -Redundant -Not ambiguous -Stop codons -AUG - start -Universal (nearly) Marshal W. Nirenberg The Dictionary Punch tape tRNA mRNA Ribosome tRNA brings in the amino acides Translation Translation Translation Translation Translation Translation Universal (nearly) Reading frames Reading frames the red dog ate the bug her edd oga tet heb ug