1. Intro to DNA – Refresher Tasks
Draw the structure of DNA.
Identify the 4 base pairs found in DNA.
List are the major differences between DNA & RNA.
Identify the chemical components of DNA.
Identify the role DNA plays in our bodies.

2. Lesson Goals – Intro to DNA
Identify and describe the chemical components of DNA.
Discuss the experiments leading to the identification of DNA as the molecule that carries genetic code.
Describe the steps leading to the development of the double – helix model of DNA.

3. Chargaff’s rule Percentages of bases in five organisms:
Analyze the data from Chargaff’s studies. What do you notice about the ratio of base pairs between the vastly different organisms?
Use math: if an organism has 33% A bases, what does this mean about the amount of G in the organisms genetic sequence.
Source of DNA A T G C
Streptococcus
29.8
31.6
20.5
18.0
Yeast
31.3
32.9
18.7
17.1
Herring
27.8
27.5
22.2
22.6
Human
30.9
29.4
19.9
19.8
E.coli
24.7
23.6
26.0
25.7

4. Assessment Questions List the chemical components of DNA.
Why are hydrogen bonds so essential in the structure of DNA?
Describe the discoveries that led to the modelling of DNA
Describe Watson and Crick’s model of the DNA molecule.
Did Watson and Crick’s model account for the equal amounts of thymine and adenine in DNA? Explain.