Name:
Student Exploration: Building DNA
Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.
Vocabulary: double helix, DNA, enzyme,
...
Name:
Student Exploration: Building DNA
Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.
Vocabulary: double helix, DNA, enzyme, mutation, nitrogenous base, nucleoside, nucleotide, DNA replication, purine, pyrimidine
Prior Knowledge Questions (Do these BEFORE beginning the Gizmo.)
DNA is an incredible molecule that forms the basis of life on Earth. DNA molecules contain instructions for building every living organism on Earth, from the tiniest bacterium to a massive blue whale. DNA also has the ability to replicate, or make copies, of itself. This process is called DNA replication & allows living things to grow and reproduce.
1. Look at the DNA molecule shown at right. Describe what its shape looks like to you.
This shape has been described as a double helix.
2. Based on this picture, make a prediction as to how a DNA molecule makes a copy of itself? (Hint: Look at the bottom two “rungs” of the ladder.)
Gizmo Warm-up
The Building DNA Gizmo allows you to construct a DNA molecule and go through the process of DNA replication. Examine the components that make up a DNA molecule.
1. What are the two main DNA components shown in the Gizmo?
2. A nucleoside has is composed of a 5-carbon sugar (deoxyribose) shown as light green and a nitrogenous base shown in various colors. When a nucleoside is joined to a phosphate, it is called a nucleotide.
How many different nitrogenous bases do you see?
The names of these nitrogenous bases are adenine (A- red), cytosine (C- yellow), guanine (G- blue), and thymine (T- green). Are all four of the bases the same size and shape?
You probably noticed that the four bases have different shapes and sizes; specifically, two of the bases are longer than the other two bases. The reason for the difference in length is their structure; the longer bases are composed of two rings, while the shorter bases are composed of one ring. See the diagrams below for a more detailed look:
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PURINES PYRIMIDINES
Notice there is a name for each of these two groups of nitrogenous bases: purines and pyrimidines. Based on this information, fill in the chart below to indicate which bases fall into these two categories. (hint: remember the LONGER bases are purines; SHORTER are pyrimidines!)
PURINES PYRIMIDINES
Notice that every base pair is composed of one purine and one pyrimidine, making the length of every base pair uniform (the same).
Question: What is the structure of DNA?
1. Build: To build a DNA molecule, drag one nucleoside over to the left (any one you like). Next, drag a phosphate over and add it to the nucleoside. Continue to alternate phosphates & nucleosides until you have used up all the materials available.
2. Once you build the left side of the molecule, more materials will appear. Use these to build the complementary strand (remember base-pairing rules!) Stop when the hint reads: “The DNA molecule is complete.”
3. In the table (right), list the sequence of bases that you created on the left- hand side of the DNA molecule and the right-hand side.
4. Take a picture:
Click the camera ( ) to take a snapshot of your DNA molecule. Right-click the image
and select Copy Image. Paste the image into the box on the next page, under the label “Original DNA molecule.” Shrink the image to fit in the box.
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