1. DNA Structure and Replication
Cell
Nucleus
Chromosomes
DNA
Biology 1-2

2. Essential Questions/Objectives
What is DNA?
How does it copy itself before cells divide?
Explain the structure of DNA.

3. James Watson and Francis Crick:
Discovered the structure
of DNA in 1953.
Discussed
probable mode of replication.

4. DNA Replication (In the Nucleus)

5. Complementary Strands Separate

6. Parent Strands Serve as Template

7. Nucleotides connected

8. What’s a Nucleotide?
Phosphate
Base
Sugar

9. DNA includes 4 nitrogenous bases:
Adenine pairs
with Thymine
Guanine pairs
with Cytosine

10. DNA is double stranded:
Hydrogen bond connects
the base pairs.
Double Helix

11. D = Deoxyribose
Pentose
Sugar:
5 sides

12. Deoxyribose Nucleic Acid (DNA)
Phosphate Group
Adenine P A
Thymine P
Nucleotide
Nitrogenous Base T
deoxyribose
Pentose Sugar P
Hydrogen Bonds P
Cytosine
Guanine C G

13. DNA Model P G A T P S A S P S C P S T P

14. DNA Components Backbone components: Sugar (deoxyribose)
Phosphate group
Bases: Adenine, Thymine, Cytosine, Guanine
Base Pairs:
Adenine and Thymine always pair up with 2 hydrogen bonds.
Cytosine and Guanine always pair up with 3 hydrogen bonds.

15. DNA Structure Quiz
Use the key on the right to construct a model of DNA showing 4 base pair matches. On the finished model circle and label one nucleotide and show where hydrogen bonds are located.
 Also, in writing or with a drawing show how your model of DNA would replicate and what the finished product of one replication would be.
= phosphate
= adenine
= cytosine
= guanine
= thymine
= sugar (deoxyribose)