1. Discovery of DNA
By Sonali Patel

2. Friedrich Miescher 1869 was the starting point of DNA discovery.
Swiss Chemist Friedrich Miescher was the first to identify DNA as an important unique molecule.
Identified nuclein
Experimental process leading to the discovery of unknown chemical properties using pus.
Goal: Isolate and characterize proteins

3. Phoebus Levene
- Discovered DNA components of a single nucleotide which included: phosphates, sugars, bases as well as ribose.
- Identified how RNA and DNA are put together
- Levene’s Polynucleotide Model
- In 1919 proposed that nucleic acids were composed of nucleotides.
- Tetranucleotide structure
Nitrogenous bases: Adenine and guanine = Purines
Cytosine and Thymine = Pyridines.

4. Ervin Chargaff
- Biochemist that expanded on Levene’s work researching for additional details of DNA structure.
- Developed a new paper chromatography method
Difference between species
- A+T= C+T
- Chargaff’s research was the backbone for Watson and Crick

5. Rosalind Franklin - Researcher at King’s College London in biophysics
- Well known for studying DNA
- Teamwork discovery with Raymond Gosling
- Photograph 51
The dark spots at the top and bottom of the image represent DNA bases.
The dark spots making the cross indicate that there is a helical form.
Photograph 51

6. Linus Pauling - Discovered the structure of proteins
- Used origami to get a visual understanding of protein, amino acid layout
- His work contributed to Watson and Crick’s discovery

7. Watson and Crick
- The discovery of the double helix occurred in 1953 by Watson and Crick.
- Research indicates that DNA consists of two polynucleotide chains that are made of 4 nucleotide subunits.
- There are hydrogen bonds between the nucleotides holding the two chains together, and these nucleotides are composed of a 5 carbon sugar.

8. Nikolai Kolstov
- Russian Biologist father of modern genetics and pioneer of biotechnology
- Career as a Zoologist, studying the anatomy of vertebrates.
- First pioneer of the cytoskeleton
- Founder of the Institute of Experimental Biology in 1917

9. Frederick Griffith
Frederick Griffith was a British Bacteriologist that was looking to develop a vaccine that worked against pneumonia.
- Usage of 2 strains of Streptococcus pneumoniae bacteria and mice.
- R strain (rough) was known to be non- virulent bacteria.
- S strain (smooth) was known to be virulent bacteria
- Results showed that R-strain bacteria are able to transform to S bacteria from heat- killed S bacteria. Thus known as the Transforming Principle

10. Hereditary Components
- “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” – Watson and Crick
- DNA encodes information through the order or sequence of the nucleotides along each strand.
- The genetic information stored in an organism’s DNA contains the instructions for all the proteins the organism will ever synthesize.

11. Works Cited
- Behind the picture: Photo 51, MRC: Medical Research Council, 25 Apr
- Carr, Steven M. Watson and Crick Model of DNA, Memorial University, 2016.
- Cold Logic, Linus Pauling the Structure of Proteins, Accessed 9 Sept
- O'Connor, C. (2008) Isolating hereditary material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase. Nature Education 1(1):105
- Pray, L. (2008) Discovery of DNA structure and function: Watson and Crick. Nature Education 1(1):100
- Rosalind Franklin Biography, Biography, 23 June 2019.
- The History of DNA Timeline, DNA Worldwide, 2014.
- Watson, James D., and Francis H. Crick. A Structure for Deoxyribose Nucleic Acid. Vol. 171, 1953, pp