1. Scientists and their contributions to the theory of the DNA molecule

2. The following scientists contributed to the theory of the DNA molecule: Friedrich Miescher Friedrich Miescher Phoebus Levene Phoebus Levene Frederick Griffith Frederick Griffith Joachim Hammerling Joachim Hammerling Avery, MacLeod and McCarty Avery, MacLeod and McCarty Erwin Chargaff Erwin Chargaff Hershey et Chase Hershey et Chase Wilkins and Franklin Wilkins and Franklin James Watson et Francis Crick James Watson et Francis Crick Crick and co-workers Crick and co-workers

3. Friedrich Miescher 1869 -Swiss scientist Friedrich Miescher was the first person to isolate the material in the nucleus that had an acid nature. He called it nucleic acid. 1869 -Swiss scientist Friedrich Miescher was the first person to isolate the material in the nucleus that had an acid nature. He called it nucleic acid.

4. Phoebus Levene 1920's – P.A. Levene determined that nucleic acid contained deoxyribose sugar, a phosphate group, and 4 nitrogenous bases. 1920's – P.A. Levene determined that nucleic acid contained deoxyribose sugar, a phosphate group, and 4 nitrogenous bases. He didn’t know the exact molecular arrangement, but he did know that one sugar, one phosphate and one nitrogenous base linked together to form a unit (he called this unit a nucleotide). He didn’t know the exact molecular arrangement, but he did know that one sugar, one phosphate and one nitrogenous base linked together to form a unit (he called this unit a nucleotide).

5. Frederick Griffith 1928 - Frederick Griffith was trying to find a vaccine for pneumonia when he found that “something” transformed the harmless bacteria into the harmful bacteria. It was later determined that this “something” was DNA. 1928 - Frederick Griffith was trying to find a vaccine for pneumonia when he found that “something” transformed the harmless bacteria into the harmful bacteria. It was later determined that this “something” was DNA.

6. Joachim Hammerling 1930s – Joachim Hammerling hypothesized that hereditary information is stored in the nucleus. 1930s – Joachim Hammerling hypothesized that hereditary information is stored in the nucleus. He experimented with green algae and observed that regeneration of new appendages was driven by the nucleus-containing “foot” of the alga.

7. Avery, MacLeod, et McCarty 1944 - Avery, MacLeod, et McCarty identified DNA as the transforming material in Griffith’s experiment on bacteria. 1944 - Avery, MacLeod, et McCarty identified DNA as the transforming material in Griffith’s experiment on bacteria.

8. Erwin Chargaff 1951- Chargaff determined that the amount of adenine equalled the amount of thymine and the amount of guanine equalled the amount of cytosine. 1951- Chargaff determined that the amount of adenine equalled the amount of thymine and the amount of guanine equalled the amount of cytosine. This is known as the « Rule of Chargaff » This is known as the « Rule of Chargaff »

9. Hershey et Chase 1952 - Al Hershey & Martha Chase used viruses which attack bacteria (bacteriophages) to show that it is only the DNA from the phage that enters the bacteria and takes control, not the entire phage. 1952 - Al Hershey & Martha Chase used viruses which attack bacteria (bacteriophages) to show that it is only the DNA from the phage that enters the bacteria and takes control, not the entire phage.

10. Wilkins and Franklin 1953 - Maurice Wilkins and Rosalind Franklin (both radiologists) gave Watson & Crick the most important information that helped them solve the DNA riddle -> X-ray data that showed the repeating units of DNA formed a double helix. 1953 - Maurice Wilkins and Rosalind Franklin (both radiologists) gave Watson & Crick the most important information that helped them solve the DNA riddle -> X-ray data that showed the repeating units of DNA formed a double helix.

11. James Watson and Francis Crick 1953- Watson and Crick determined the double helix arrangement of DNA (Cambridge, England) 1953- Watson and Crick determined the double helix arrangement of DNA (Cambridge, England) The DNA double helix model was intorduced to the world in the magazine Nature in 1953. The DNA double helix model was intorduced to the world in the magazine Nature in 1953.

12. Francis Crick and Co-workers 1961 - Francis Crick & coworkers discovered the triplet codon that codes for an amino acid during protein synthesis. 1961 - Francis Crick & coworkers discovered the triplet codon that codes for an amino acid during protein synthesis.

13. DNA molecule