DNA Webquest
Name___________________
Visit the following websites to explore how experiments produced clues to the
structure of DNA or RNA. Learn about the relationship between the structure of
nucleic acids and their functions.
Objectives: Students will be able to
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analyze experiments that contributed to current understanding of DNA
structure for important clues.
explain how base pair rules effect the forming of the rungs in DNA.
compare the shapes of the nucleotides to explain how hydrogen bonds are
formed that hold base pairs together.
describe the process of DNA replication.
1. Explore the DNAinteractive Finding the Structure webpages.
http://www.dnai.org/a/index.html
Watch an interview for each scientist. Click on pieces of the puzzle to
examine the evidence for clues to the structure of DNA.
Rosalind Franklin—X-ray: describe how
the pattern of the x-ray diffraction from
the side gives clues to the structure.
Would a view at the end of the molecule
give any clues? __________________
_______________________________
_______________________________
_______________________________
_______________________________
Linus Pauling—triple helix: What was the
key piece of information works against the
triple helix model?
______________________________________________
Sugar-phosphate
backbones
______________________________________________
______________________________________________
______________________________________________
Which type of helix works with the data?
(circle one: single, double, or triple)
bases
Watson and Crick—models: Which bases did their work predict would pair
together?
a. Adenine and cytosine + guanine and thymine
b. Adenine and thymine + guanine and cytosine
c. Adenine and guanine + cytosine and thymine
Name the two characteristics of the bases they used to make the model.
1.____________________________________________________________
2.____________________________________________________________
Erwin Chargaff—base pair rule: Was the ratio of A to T and G to C consistent
with the model developed by Watson and Crick? Why? _________________
_____________________________________________________________
_____________________________________________________________
2. Explore the structure of DNA. Use the Learn more about buttons. Rotate
the molecule and use the atom button to locate where the carbon, nitrogen,
oxygen, phosphorous, and hydrogen atoms are found.
http://www.pbs.org/wnet/dna/dna_explorer/index2.html
a. to explore the bases
b. to explore the sugar/phosphate backbone
Which compounds form the backbone? 1._________________________________
2._________________________________
Which type of compound forms the rungs? ________________________________
Label the parts of the DNA molecule.
The smaller nitrogenous bases are
pyrimidines called:
C is _________________________
T is _________________________
The larger nitrogenous bases are
purines called:
G is _________________________
A is _________________________
In DNA, the phosphate is negatively
charged and bonds to a sugar called
_____________________________
Compare the number of hydrogen
bonds between C-G and T-A____________________________________________
3. Build a DNA Molecule at:
http://learn.genetics.utah.edu/content/molecules/builddna/
Complete assembly of a section of DNA. Proceed down the page to read
more about DNA.
Which bases bond together to form the rungs of the DNA molecule?
_____________________________________________________________
Why do these bases form pairs? Why would other combinations not work
well? _________________________________________________________
_____________________________________________________________
4. Click the link for DNA unzip. http://www.dnalc.org/resources/3d/23-dnaunzip.html
What shape does DNA have before the process of replication begins?
_____________________________________________________________
How does the sequence of ATGC in one strand allow construction of a second
strand? _______________________________________________________
_____________________________________________________________
_____________________________________________________________
What is the term for the strand that can form hydrogen bonds to the
original?
_____________________________________________________________
5. Click the link for the Mechanism of Replication (basic) at the bottom of the
page in the right hand column and answer the following questions.
An enzyme ________________ the DNA into _____________ strands to
prepare for replication.
6. Click the Copying the Code button, Pieces of the Puzzle, and find Semiconservative replication puzzle piece. http://www.dnai.org/a/index.html
The original strands _____.
a. Both originals go into the same molecule and an all new molecule is
formed. Conservative model
b. Are broken down and the original nucleotide sections used to construct
two new molecules.
c. Are separated and each becomes the template for building the
complementary strand in new molecules. Semiconservative model
Additional Resources:
A Reader’s Guide to the Double Helix, Brown University,
http://www.brown.edu/Courses/BI0020_Miller/dh/guide.html
Linus Pauling and the Race for DNA, Oregon State University,
http://scarc.library.oregonstate.edu/coll/pauling/dna/video/1973v.3.html
DNA Replication, PBS Learning Media,
http://www.pbslearningmedia.org/resource/biot11.sci.life.gen.structureofdna
/the-structure-of-dna/
The Talking Glossary of Terms, National Human Genome Research Institute,
National Institutes of Health, http://www.genome.gov/Glossary/
Transcribe and Translate a Gene, Learn.Genetics, Genetic Science Learning
Center, University of Utah,
http://learn.genetics.utah.edu/content/molecules/transcribe/
e-Books and Article Library, Scitable, natureEducation,
http://www.nature.com/scitable/topic/genetics-5
3-D Animation Library, Cold Spring Harbor Laboratory,
http://www.dnalc.org/resources/3d/
DNA Workshop (shockwave animation), PBS,
http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html