Transcript Section 12-1 - SchoolNotes
Section 12-1 Discovery of DNA Griffith’s Transforming Factor (1928) Griffith’s Transforming Factor (1928) Harmless R strain + killed S strain did not cause pneumonia on their own; but did when mixed together. The harmless bacteria must have picked up the disease-causing trait from the killed strain transformation. Avery continues the work (1944) Used enzymes to break down proteins, lipids, carbs, RNA, and DNA in bacteria. Transformation stopped only when DNA was broken down DNA had genetic info. Hershey and Chase and Bacteriophages (1952) Debate continued on whether protein or DNA was the hereditary info of living things. Hershey and Chase used a simple virus (made of only protein and DNA) and radioactive markers to trace genetic material. Convinced the world that DNA (not protein) was genetic material. DNA Structure Discovered (1953) J. Watson and F. Crick (with help of R. Franklin) describe DNA as a chain of nucleotides arranged in a “double helix”. (Watson, Crick, and M. Wilkins share Nobel Prize in 1962.) Nucleotide Structure Nucleotides: small units that make up a chain of DNA. Include: 1) phosphate group 2) sugar (deoxyribose) 3) nitrogen base (A, T, C, G) The Double Helix Two nucleotide chains connect with hydrogen bonds between the nitrogen bases; then twist into a spiral. Chargaff’s Rule: Adenine pairs with Thymine; Cytosine pairs with Guanine.