1. DNA’s Discovery and Structure

2. Scientists that determined DNA’s Structure and Importance 1866 Gregor Mendel – demonstrated that parents pass traits to offspring-thought traits contained in a molecule 1869 Friedrich Meisher – Isolated DNA from cell nucleus – named it nucleic acid 1889 R.A. Altman-determined the chemical composition of DNA

3. Scientists that Determined DNA’s Structure and Importance 1919 Phoebus Levene – Determined the structure of a DNA nucleotide – first to propose that DNA was a polymer made of nucleotides P = Phosphate S= 5C sugar B= Nitrogen base

4. Scientists that Determined DNA’s Structure and Importance 1928 Frederick Griffith – bacterial transformation – traits passed by a chemical “transforming principle”

5. Scientists that Determined DNA’s Structure and Importance 1944 Oswald Avery – DNA = key to transformation - Avery and his partners conducted experiments which proved that DNA was Griffith’s “transforming principle”

6. Scientists that Determined DNA’s Structure and Importance 1949 Erwin Chargaff – base-pairing rules %Adenine=%Thymine %Guanine=%Cytosine 1952 Alfred Hershey & Martha Chase – Radioactive labeled Bacteriophage transformation experiment-settled DNA-protein debate

7. Hershey & Chase

8. Important Scientists in the “Race for the Double Helix” 1952Maurice Wilkins & Rosalind Franklin – X-ray diffraction- “photographs” of DNA – DNA must be a some type of spiral (helix) – DNA’s diameter is constant and stable

9. Important Scientists in the “Race for the Double Helix” 1953 James Watson & Francis Crick – Created the first accurate 3-D model of DNA – Won the Nobel Prize with Wilkins

10. DNA’s Structure DNA is composed of nucleotides DNA contains four nitrogen bases: adenine(A) cytosine(C) guanine(G) thymine (T) A & G are purines C & T are pyrimidines

11. DNA’s Structure DNA is a double helix -2 strands of DNA nucleotides joined to form a “twisted ladder” -the strands are held by hydrogen bonds between the nitrogen bases

12. Chargaff’s Rule The nitrogen bases form the “steps” on the DNA ladder by complementary pairing A == T C == G T == A G == C A == T A always pairs with T T == A C always pairs with G Sugar- phosphate backbone

13. Central Dogma of Molecular Biology 1958 Francis Crick proposed: DNA codes for the production of RNA RNA codes for the production of protein Protein does not code for the production of protein DNA or RNA “Once information has passed into protein it cannot get back out again”

14. Vocabulary: Mendel, Meischer, Altman, Levene, Griffith, Avery, Chargaff, Hershey & Chase, Franklin & Wilkins, Watson & Crick, nucleotide, deoxyribose, deoxyribonucleic acid complementary base pairing, double helix, Central Dogma of Molecular Biology