Student Exploration: Building DNA
Vocabulary: double helix, DNA, enzyme, lagging strand, leading strand, mutation, nitrogenous base, nucleoside, nucleotide, replication
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
DNA is an incredible molecule that forms the basis of life on Earth. DNA molecules have instructions for building every living organism on Earth, from the tiniest bacterium to a massive blue whale. DNA also can replicate or make copies of itself. This allows living things to grow and reproduce.
Look at the DNA molecule shown at right. What does it look like? The shape to the right looks like a spiral staircase.
This shape is called a double helix.
Based on this picture, how do you think a DNA molecule makes a copy of itself? (Hint: Look at the bottom two “rungs” of the ladder.) I think that the DNA molecule would split down the middle and copy itself.
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.
What are the two DNA components shown in the Gizmo?
A nucleoside has two parts: a pentagonal sugar (deoxyribose) and a (in color). When a nucleoside is joined to a phosphate, it is called a .
How many different nitrogenous bases do you see? 4
Note: The names of these nitrogenous bases are adenine (red), cytosine (yellow), guanine (blue), and thymine (green).
Build a DNA molecule
Get the Gizmo ready:
If necessary, click Reset to start the building process.
Question: What is the structure of DNA?
Build: Follow the steps given in the Gizmo to construct a molecule of DNA. (Note: For simplicity, this DNA molecule is shown in two dimensions, without the twist.)
Stop when the hint reads: “The DNA molecule is complete.” In the spaces at right, list the sequence of nitrogenous bases on the left-hand strand, called the , and the right-hand strand, called the .