Download Activity 3.3.4 DNA Models

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Activity 3.3.4 – DNA Models
Purpose
Different types of molecules combine to create DNA. A strand of DNA looks like a
ladder. DNA is formed by nitrogen molecules linking together to make nucleotides.
Nucleotides include cytosine, thymine, adenine, and guanine and these compounds
form the rungs, or steps of the DNA ladder. Phosphoric acid and sugar make the
frame of the ladder. All of these molecules combine in specific patterns that enable
DNA to be replicated to facilitate cell division.
Let’s create some DNA. Do you remember the components of DNA and how these
components are arranged? Take out your Presentation Notes from the DNA
PowerPoint® presentation to help you complete this activity.
Materials
Per pair of students:
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Per student:
Lab-Aids® DNA Model Packet
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Pencil
Agriscience Notebook
Procedure
You and a partner will be building a model of a DNA strand. The objective is to
assemble the color-coded model pieces representing molecules according to the
appropriate bonds that are formed in real DNA strands. Once you have successfully
built a DNA model, you will simulate how DNA strands replicate.
Part One – DNA Model Building
1. Open a Lab-Aids® DNA Model Packet and separate the pieces by color.
2. In the DNA Model Packet you will find several pieces that represent the following
molecule compounds:
Nitrogen Bases – create the rungs of the DNA molecule
 BLUE tubing = Cytosine (C)
 GREEN tubing = Thymine (T)
 ORANGE tubing = Adenine (A)
 YELLOW tubing = Guanine (G)
 WHITE solid rod = Hydrogen bond to link nitrogen bases together to form
nucleotides
Curriculum for Agricultural Science Education – Copyright 2011
AFNR – Unit 3 – Lesson 3.3 – Activity 3.3.4 - DNA Models – Page 1
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DNA Strand Framework – create the side rails of the DNA molecule
 WHITE tubing = Phosphate group
 BLACK linkage = Deoxyribose sugar group
3. Create the strands of the DNA molecule by connecting the phosphate groups to
deoxyribose sugar groups. The strands are the side rails of the DNA ladder and
phosphates and deoxyribose sugar groups assemble in an alternating pattern.
You want to create two strands consisting of eight deoxyribose sugar bonds.
4. On one strand of DNA created in Step 3 above, randomly attach nitrogen bases
to the deoxyribose sugar molecule. You can mix the different types of nitrogen
bases up depending on whatever pattern you wish to create.
5. Insert a hydrogen bond in each nitrogen base attached to the DNA strand.
6. Attach the appropriate nitrogen base pairing to the hydrogen bond. Remember to
refer to your Presentation Notes for the base-pairing rule.
7. Complete the double helix DNA model by attaching the second DNA strand to
the free end of the nitrogen base pairing.
8. You now have created a DNA model that resembles a ladder. DNA, although
microscopic, is very abundant in a nucleus. There is so much DNA in a nucleus
that the strands twist and wrap themselves inside the nuclear membrane. You
can replicate this by twisting your model to make it become three-dimensional
rather than a flat two-dimensional shape.
9. Double check to ensure that you have followed the pairing rules for the nitrogen
bases. Your teacher will need to verify that you have completed this part of the
model correctly.
Teacher’s Signature for Part
One – DNA Model Building
Part Two – DNA Replication Simulation
1. Using your model created in Part 1, unzip the hydrogen bonds for half of your
model.
2. Add additional hydrogen bonds to the newly created open ends of the tubing.
3. Replicate the DNA strand by attaching the appropriate nitrogen base to the free
end of the hydrogen bond according to the base-pairing rule.
4. Continue to unzip and complete the DNA replication process for the remaining
DNA nucleotides from the original model.
5. You should now have two identical double helix strands of DNA. Have your
teacher verify that you did this procedure correctly.
Teacher’s Signature for Part
Two – DNA Replication
Curriculum for Agricultural Science Education – Copyright 2011
AFNR – Unit 3 – Lesson 3.3 – Activity 3.3.4 - DNA Models – Page 2
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Conclusion
1. Explain the base pairing rule for nitrogen bases of DNA.
2. Based on what you have learned, explain how DNA is replicated in a cell.
Curriculum for Agricultural Science Education – Copyright 2011
AFNR – Unit 3 – Lesson 3.3 – Activity 3.3.4 - DNA Models – Page 3