1. BIOLOGY CHAPTER 8 FROM DNA TO PROTEINS
SECTION 8.1 ON IDENTIFYING DNA AS THE GENETIC MATERIAL

2. 8.1 Griffith’s Transforming Principle
In 1928, Griffith was a British microbiologist who was studying the bacterium that causes pneumonia (streptococcus pneumoniae)
Two forms of the bacteria exist– smooth (s) and rough (r)
Smooth form is deadly to mice
Killed S did not harm mice
Rough bacteria did not kill the mice

3. Transformation
When injected with a combination of the live Rough and dead Smooth the mice died
Also, live Smooth bacteria were found in the blood of the dead mice.
Conclusion: Somehow the non-lethal Rough bacteria had TRANSFORMED into deadly Smooth bacteria.
Genetic material from S had gotten into R and transformed it into S

4. Oswald Avery
In 1944, Another scientist named Oswald Avery devised a clever experiment with chemical analysis
Avery’s chemical analysis showed that the transforming agent was probably genetic material not protein
Scientists were still skeptical

5. Hershey and Chase confirm DNA as the genetic material
A bacteriophage (also called a phage) is a virus that attacks bacteria by injecting its genetic material (DNA) into the bacteria
It is DNA surrounded by a protein coat
In 1952, Hershey & Chase used phages & radioactive isotopes which only show up in DNA to successfully support their hypothesis

6. Additional History
In the 1950s, Rosalind Franklin ( ), was a British scientist who was doing X-ray diffraction studies on DNA
Her coworker Maurice Wilkins showed her work to two other DNA American researchers without her permission
Those two – Watson and Cricks – took her work and figured out the structure of DNA – a double helix
The three of them got the Nobel Prize and Franklin, who had died in 1957, was not even mentioned

7. What makes up a nucleotide?
Based on this history, the make up of a nucleotide (the monomer for nucleic acids) became known to have :
1. A Phosphate group (PO4)
2. A ring-shaped, 5 carbon sugar called deoxyribose (remember – anything ending in “ose” is a sugar)
3. A nitrogenous base consisting of a single or double ring built around C and N atoms

8. Chargaff’s Rule The four nitrogenous bases in DNA are: - THYMINE (T)
- ADENINE (A)
- GUANINE (G)
- CYTOSINE (C)
CHARGAFF’S RULE of BASE PAIRING states that Adenine always pairs with Thymine; and Guanine always pairs with Cytosine
A-T and C-G