1. Leads to DNA: Griffith’s Experiment
In 1928, Frederick Griffith was trying to figure out why people got sick.
Some factor transformed the harmless bacteria into harmful ones.
Genetic information could be transferred from one bacteria to another called transformation.

2. Leads to DNA: Avery’s experiment
Found that Nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.
He found that Protein destroying enzymes did not affect transformation.
Many still believed proteins were the source of genetic material…

3. Leads to DNA: Hershey & Chase
Studied Viruses
Used radioactive markers to see what was injected into cells by viruses
Phosphorus (found in DNA)
Sulfur (found in proteins)
Phosphorus was found in cells
Found that genetic material was DNA, not protein.

4. Chargaff’s Rules Chargaff’s rules (1949) found the following:
That for every A paired with T.
and for every G paired with C.
This varied between different types of organisms.

6. Leads to DNA: Rosalind Franklin
Using DNA diffraction, Rosalind Franklin used high energy X-rays beamed at DNA samples and found the shape of DNA.
Showed that the strands of DNA are twisted around each other in a helix.
The X suggests there are two strands in the structure.
(She died at age 37 of Ovarian cancer, and during her research (after her father forbid her to be a scientist) was forbidden from male pubs and continued research while her male counterparts went to male-only pubs.)

7. The Double Helix: Watson & Crick
James Watson and Francis Crick saw Rosalind’s research and determined the model of DNA.
That means the DNA code had a specific code of base pairing.
April 1953.
Purines: Adenine and Guanine
Pyrimidines: Cytosine and Thymine

8. What is DNA? DNA = Deoxyribose Nucleic Acid
Code of Life – codes for proteins essential to the health of the organism.
Backbone made of alternating Phosphorus and Sugars
Made of matching Nitrogen bases
Adenine to Tyrosine
Cytosine to Guanine

9. What is the structure of DNA?
DNA is composed of Nitrogen bases, (ATGC) anchored to a deoxyribose sugar along a Phosphate backbone.
Nucleotides = 5 carbon sugar, phosphate and a Nitrogen base.
Each nitrogen base is bonded by weak Hydrogen Bonds.
Those bonds are weak for DNA to replicate or transcribe.