1. The Structure of dnA Big Q: What are the chemical components of DNA?
Big Q: What clues helped scientists solve the structure of DNA?
Big Q: What does the double helix model tell us about DNA?

2. Engage - Describe the sculpture
What is the structure of DNA and how does it function in genetic inheritance?

3. Explain - The components of DNA
The building blocks of DNA are called nucleotides.
Parts of a nucleotide:
1. deoxyribose sugar
2. nitrogenous bases
3. phosphate group
There are four types of nitrogenous bases in DNA:
Guanine
Adenine
Thymine
Cytosine

4. Explain - Nitrogenous bases
Purine Structure:
Pyrimidine Structure:
Double rings
A purine must bind to a pyrimidine:
A - T G - C
T - A C - G
Single ring

5. Elaborate - Chargaff’s Rule
Erwin Chargaff discovered the ratio of nitrogenous bases in DNA
Chargaff’s Rule - the percentage of A will be the same as the percentage of T in a DNA strand. The percentage of C will be the same as the percentage of G in a DNA strand.
If 20% of your DNA consists of T, how much A do you have?
20%

6. Elaborate - Base Percentages
Analyze the data on the worksheet using Chargaff’s Rule.
***Answer all questions on your worksheet.

7. Explore - The history of DNA Structure
Rosalind Franklin - British scientist famous for discovering the helix structure of DNA
Watson and Crick - discovered all the parts of DNA based on Franklin’s picture
Watson + Crick
X-Ray Diffraction

8. Explore - DNA models
If a twisted ladder is used as a model of DNA, which parts of the DNA correspond to the sides of the ladder?
What parts of the DNA correspond to the rungs of the ladder?

9. Elaborate - Check for Understanding
How is solving the puzzle of DNA’s structure an example of a collection of discoveries by different scientists?

10. Explain - the double helix model
What did these scientists discover about the model?
1. Antiparallel Strands - run in opposite directions
2. Hydrogen Bonding - weak bonds hold DNA together
3. Base Pairing - A and T, G and C

11. Elaborate - DNA Modeling
Students will create their own models of DNA
***Answer all questions in your lab packet