Names:____________________________________________________ Date:_____________
DNA Replication Activity
Introduction: DNA is the blueprint of life. It carries the instructions for making all of the
proteins the body will need that are specific for each individual. DNA is a very long, polymer
made up of monomers called nucleotides. Each nucleotide includes three parts: sugar,
phosphate and nitrogenous base. DNA in eukaryotes is double stranded forming a double helix,
it resembles a twisted ladder. The sides or legs of the ladder are analogous to the sugarphosphate backbone of DNA. The rungs of the ladder are analogous to the nitrogenous bases
linked by hydrogen bonds. In the lab, you will construct a molecule of DNA and model what
occurs during DNA replication.
Purpose: To review the molecular make-up of DNA and how it relates to the process of DNA
replication.
Materials: a kit including:
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Nitrogen bases: cytosine (blue), thymine (green), adenine (orange), guanine (yellow)
Deoxyribose sugars: black pentagons
Phosphate: white tubes
Hydrogen bonds: white sticks
Procedure:
1. Build one side of a DNA ladder constructed of 9 nucleotides. Each DNA molecule is
different, so it is your choice on which bases to include and in what order.
2. Next build the second side of the DNA ladder which would be COMPLEMENTARY to the
first side you made. Use Chargaff’s rules for base-pairing.
3. Connect the two strands of DNA together with hydrogen bonds between the
complementary bases.
4. Draw your strand in the appropriate box on the next page. 1st Teacher check off: _____
5. Unzip the two strands as occurs in the first step of DNA replication by breaking the
hydrogen bonds between the two strands.
6. Now, build a new strand for each of the original strands, again making sure the bases
are paired up correctly between the original and new strand.
7. You should end up with 4 strands (2 original and 2 new). Connect one original and new
strand together, then repeat with the other two strands. The two DNA strands should be
identical copies of each other!
8. DNA replication is now complete. Draw your two new strands of DNA in the appropriate
box on the next page.
9. DON’T DISMANTLE until your teacher checks you off. 2nd Teacher check off: ______
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Drawing of First Model
Drawing of Second 2 Models
Questions:
1. What does the cell use DNA for?
2. What are the monomers of DNA called and what are the 3 components of them?
3. What are the two structural categories that nitrogenous bases fall into?
4. List the four nitrogenous bases and its structural category.
5. What two components of DNA are like the “sides of a ladder?”
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6. What components of DNA are like the “rungs of a ladder?”
7. Describe the first step in DNA replication.
8. What is the name of the enzyme that unzips the DNA?
9. What is broken in the DNA ladder in order for it to unzip?
10. Describe the second step in DNA replication.
11. Explain Chargaff’s base-pairing rule.
12. If 40% of a DNA molecule is adenine, what percent is cytosine?
13. Describe the third step in DNA replication.
14. What molecule puts the complementary bases together and checks for errors?
15. What process can now happen once DNA has been replicated?
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