Download Activity 4.1.4 DNA Models

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Activity 4.1.4 DNA Models
Purpose
Different types of molecules combine to build 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 build some DNA. Do you remember the components of DNA and how these components are
arranged?
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. Take
out your Presentation Notes from the DNA PowerPoint® presentation to help you complete this activity.
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 – build the rungs of the DNA molecule
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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
DNA Strand Framework – build the side rails of the DNA molecule
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WHITE tubing = Phosphate group
BLACK linkage = Deoxyribose sugar group
3. Build 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. Build two strands consisting of eight deoxyribose sugar
bonds.
Curriculum for Agricultural Science Education © 2014
AFNR – Activity 4.1.4 DNA Models – Page 1
4. On one strand of DNA made 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 build.
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 built 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 threedimensional 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 the model you built in Part 1, unzip the hydrogen bonds for half of your model.
2. Add additional hydrogen bonds to the newly formed 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
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 © 2014
AFNR – Activity 4.1.4 DNA Models – Page 2