1. Objectives:
To understand how DNA was discovered
To be able to model the structure of DNA
Journal:
What is the function of DNA?

2. The Discovery of DNA
Before the 1950s, scientists weren’t sure what genes were made of
There was a race between the best scientists in the world to figure it out
Through experiments they figured out DNA was the hereditary material

3. Experiments that Determined the Structure of DNA
Rosalind Franklin and Maurice Wilkins
Took pictures of DNA using x- ray diffraction
Chargaff
Determined amount of A = T, C=G
James Watson and Francis Crick
Built model of DNA
Credited with actually discovering DNA structure

4. Function of DNA Contains the information on how to make proteins.
Proteins are the workers to put together and run a cell.

5. Sugar Phosphate Group Nitrogen Base
Building blocks of DNA
Nucleotide Structure – basic building block of DNA
Sugar
Phosphate Group
Nitrogen Base P
Sugar
N. Base

6. Four Different Nitrogen Bases
1. Adenine
2. Guanine
3. Thymine
4. Cytosine

7. DNA Structure
Double Stranded Helix

8. Antiparallel Strands
DNA strands run antiparallel, opposite of each other
One runs from 5’ to 3’ the other runs from 3’ to 5’

9. Spiral Staircase Structure
Sides of the staircase = sugar & phosphates
Steps of the staircase = nitrogen bases.

10. Base Pairing Rule:
A – T held together by two hydrogen bonds
C – G held together by three hydrogen bonds

11. Purines vs. Pyrimidines
Pyrimindines
Structure has one ring
Cytosine and Thymine
Purines
Structure has two rings
Adenine and Guanine