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WebLab4: Exercise1
Discovering DNA: Structure and Replication
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Objectives:
- Explain why DNA is called an informational macromolecule.
- Explain the relationship between cellular DNA and such biomolecules as carbohydrates, lipids and proteins.
- Explain the relationship between DNA and genes.
- List the subunits composing DNA.
- Draw a simple diagram showing DNA's 2 sugar-phosphate chains and the attached nitrogen bases correctly paired.
- Explain the role of the enzyme, DNA Polymerase, in DNA replication.
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Materials:
- A computer, a printer, and an ISP (Internet Service Provider).
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Methods:
- Read the Background Information to help prepare you for the content of this exercise.
- Take a look at an animated, simplified three dimensional DNA molecule: go to
3D rapid rotation DNA Animation Site and 3D slower rotation DNA Animation Site compiled and generously shared on the web by Doug Lundberg.
- Another animated view, this time of a more accurate space-filling DNA model can be found at this Space-Filling DNA Animation Site, another Doug Lundberg webpage.
- Go to the DNA Construction Site entitled "What is DNA?" from the University of Utah. Read this webpage and build a DNA chain with the animation midway down the page. By exploring the site you will gain insight into DNA's significance. You will be directed to different areas of this website during this and other Weblabs.
- Answer the following questions based on your experience at the DNA Construction Site:
- Which molecules make up the "uprights" or sides of the DNA ladder?
- Which molecules make up the "rungs" or steps of the DNA ladder?
- How do the rungs hold themselves together? This is a tough questions! What is being asked is how the nitrogen bases that project to the interior of the DNA molecule, forming the ladder's rungs, attach to each other forming a complete rung?
- Are the molecules making up the two sides (uprights of the ladder)of the DNA molecule oriented in the same or in opposite directions? (What does the term "antiparallel" mean?)
- Go to the DNA-Cellular Relations page for further background information about DNA. Then continue with step 5.
- Go to the DNA Replication webpage from Brooklyn College and study the diagrams and text presented. Be sure to click on the large blue dot in the figure to study the replication process in greater detail and with greater clarity.
- Answer the following questions based on your observations and study at the DNA Replication webpage:
- When the two strands of the DNA molecule separate in preparation for replication, "special proteins" were said to unwind the molecule to expose the nitrogen (nucleotide) bases. What kind of proteins do you think these are? Structural? Enzymatic?
- Define "DNA polymerase" and explain its role in DNA replication.
- As the new DNA molecules are constructed, indicate which bases always pair.
- After you have constructed two new daughter DNA molecules, is either of the two a completely new molecule? What is the meaning of the expression "semiconservative replication?"
- As you have worked your way through this WebLab, there have been questions
you were supposed to answer. To submit the answers to these questions
to me, go to the navigation bar and click on the "contact"
icon. Fill out the required information, including the password
given to you in class, and write your answers in the answer space
provided. Your submission will reach me by email and I will respond
to you also by email and indicate your grade based on the quality
of your answers.
- Now have some fun! Go to this Artistic DNA Site imaginatively and skillfully rendered by Paul Thiessen. Look especially at "Bottled Gene" and "Mapped DNA." Click on the small images to enlarge them.
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