1. I. DNA Structure
This unit is about how DNA stores the code for making
proteins and how the code is passed on to offspring
(kids). DNA is the molecule that allows for genetic
information to be passed on from parents.

2. DNA Structure and Function
1. DNA is made of smaller, repeating units, called nucleotides
2. Each nucleotide has three parts:
a. Deoxyribose sugar b. phosphate group c. Nitrogen containing base

3. Nitrogen Bases:1 of 4 types
Adenine Guanine
Thymine Cytosine

4. 3. Bases always pair-up in the same way to
form complimentary base pairs.
Adenine - Thymine
OR
Thymine - Adenine
A - T
Guanine - Cytosine
OR
Cytosine - Guanine
G - C

5. 4. Sides of DNA are alternating sugar and
phosphate groups
Sugar/phosphate
backbone

6. 5. Nitrogen bases
- in middle of
molecule are held
together by double
or triple hydrogen
bonds*
A - T
*Hydrogen bond =
weak bond
G - C

7. 6. Shape: Double helix or twisted ladder

8. First seen like this…by Rosalind Franklin

9. PRIZE TIME: DNA Replication
If the nitrogen bases always
pair with their compliment,
then predict how DNA might
replicate.
Write it down on your notes.

10. DNA Replication: copying DNA - makes two
identical molecules
A - T G - C
T
C
C
G
G
T A
A
Helicase
enzyme
A
C
T
C
T
A
G
G
Polymerase
7. DNA is “unzipped” by helicase enzymes. Then
polymerase attaches correct nucleotides to match the
base pairs.
8. A mistake in just one base pair is a mutation.