1. DNA

2. Objectives
Draw a diagram of DNA label the six parts of DNA- Circle a nucleotide. OR make DNA Jewelry
Distinguish between a Chromosome, Chromatin, DNA and a Gene
Discuss the experiments and contributions of the groups of scientists listed below.
Griffith, Avery, and Hershey and Chase

3. Strawberry DNA
Summary:
Students will extract DNA from strawberries.
Learning goals/objectives:
Students will observe first hand that DNA is in the food that they eat. Students will learn the simple method of DNA extraction and will be able to explain the rationale of each step. Students will be able to explain why DNA extraction is important to scientists.
Prerequisites:
Students should know about the basic structure of DNA and its location.

4. The History of DNA discovery and current DNA research

9. Grffith and Transformation
A British scientist, Frederick Griffith
Wondered how certain bacteria cause pneumonia.

10. Griffith and Transformation
A British scientist, Frederick Griffith
Wondered how certain bacteria cause pneumonia.
When injected in mice, they developed Pneumonia
When injected in mice, they remained healthy

11. Griffith then heat killed the disease causing bacteria and injected it into the mice….. NO sickness!
Heat killed disease cells
When injected in mice, they developed Pneumonia
When injected in mice, they remained healthy

12. Experiment: What happens if kill bacteria and mix material with harmless bactatia? Will it cause a disease?
Yes!
Transformation: Some factor in the heat killed diseased bacteria was transferred to the harmless form.

13. What changed their nature?
Rough bacteria – a harmless form
were the only live cells given to the mice.
What changed their nature?

14. Griffith called this phenomenon “Transformation”
Some non-living material must have been responsible for changing the harmless rough into DISEASE CAUSING smooth!
Griffith theorized:
Some molecules from the (heat-killed) smooth disease causing bacteria must have been transferred to the harmless rough edge type, making them “smooth killers”.
Griffith called this phenomenon “Transformation”

15. Oswald Avery: DNA must be the molecule responsible for
1944 about 20 years later….
Oswald Avery:
Conducted experiments to determine which organic molecules are causing the transformation
Avery treated heat-killed bacteria:
with enzymes that destroyed its proteins Still cause disease!
then tried enzymes that destroyed its carbohydrates Still cause disease!
and so on and so fourth for various other organic molecules in the heat-killed cells…
Transformation was only blocked when destroyed all the DNA molecules left inside the heat-killed bacteria
cells.
DNA must be the molecule responsible for
Transformation!!

16. 1952 Alfred Hershey and Martha Chase
Studied bacteriophages – viruses that infect bacteria

19. They tagged the virus protein with radioactive sulfur and the DNA with radioactive phosphate.
They were able to watch the tagged compounds to find out which material was passed on to cause the disease.

20. Cell contains no radioactive protein
Cell contains radioactive DNA

21. The Hershey-Chase experiments convinced the scientific community that DNA, not protein, was the material of heredity.
This inspired James Watson and Francis Crick to begin their efforts to discover its structure.

22. Watson and Crick used an X-Ray of DNA taken by Rosalind Franklin to help them determine DNA structure

23. History of DNA Discovery: Summary
1920’s-1950’s: various experiments building upon each other determined that DNA is the genetic material for all life on Earth.
-Griffith and “Transformation” of harmless to disease causing
-Avery’s found DNA was responsible when destroyed all other organic compounds
-The Hershey-Chase Experiment Tagged DNA and found it was transferred by the virus
1950’s: The Structure of DNA was determined to be a double helix. - James Watson and Francis Crick constructed various models of how the DNA molecule could be structured.
- Rosalind Franklin’s x-rays of DNA helped Watson and Crick determine that the structure of DNA is the double helix.

24. DNA Structure and Replication

25. This is a model of the double helix shape of DNA.
DNA is the molecule that codes for all proteins of a cell, and transfers hereditary information from one cell to the next.
This is a model of the double helix shape of DNA.

26. DNA is called a Double helix because not only is it a helix shape, but it is made up of two strands, wound together.

27. A DNA Strand is a polymer of monomers called nucleotides.
Each nucleotide consists of:
A phosphate group
A sugar group
One of 4 bases: A, C, G, T.
The phosphates and sugars form the outer backbone
The A’s, C’s, G’s, and T’s are the inner “rungs of the ladder”.

28. The bases of the nucleotides of one strand interact with the bases of the nucleotides of the other strand.
A always pairs with T
G always pairs with C
The bases are held together by hydrogen bonds.

29. genetics.nbii.gov/ Basic1.html

30. histones
DNA
nuceleosomes
supercoil

31. DNA Replication: How more DNA molecules are made in the body.
DNA replicates according to the semi-conservative model.