INTRO TO THE STRUCTURE OF DNA
Name ______________________
DNA contains the instructions to provide all of the information necessary for an organism to grow and
live. DNA resides in the nucleus of your cells.
The instructions tell the cell the role it will play in your body. Let’s look at a set of instructions from the
inner ear cell.
http://www.hhmi.org/biointeractive/dna-packaging Watch this video to see both the structure of
chromatin, and how all that DNA fits into the nucleus
How does protein help the DNA to form a chromosome?
Now go to http://learn.genetics.utah.edu/content/molecules
Work your way through What is DNA, Build a DNA molecule, and what is a gene. You should be able to
answer all the questions 1-9 using this website, and others provided. Then complete the modeling DNA
activity.
1. There are many ways to draw DNA
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INTRO TO THE STRUCTURE OF DNA
Name ______________________
DNA is often drawn in the shape of a ladder with rungs
like the drawing shown to the right. In reality, DNA comes in
the shape of a twisted ladder that is
called a ______________________________
2.
The sides of the ladder are made of a
________________________________ backbone
3. The rungs of the ladder are made of four different
____________________. These rungs of the ladder are the molecules that actually code for
proteins that are created.
4. Identify the four bases, and using the pictures above, or the ones on the website, identify which
bases pair, and whether they pair with three bonds or with two bonds.
5. What type of bonds hold the bases together?
6. The DNA strands contain bases in a certain sequence. Copy the sequence shown on the
website. Notice that the DNA bases are always read in groups of three, called triplets.
7. Now go to the HHMI site http://www.hhmi.org/biointeractive/paired-dna-strands
And watch the animation. A gene consists of many triplets (hundreds or even thousands). A
gene is a length of DNA that codes for a protein.
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INTRO TO THE STRUCTURE OF DNA
Name ______________________
8. Now that you understand the structure of DNA, create your own molecular model of DNA,
using the model kits provided.
9. View the website on DNA replication.
http://highered.mheducation.com/sites/0072437316/student_view0/chapter14/animations.ht
ml#
When does replication (duplication) of DNA occur?
Where does it occur?
10. A diagram of DNA is shown below. Identify all the “letters” in the diagram (except for e and f).
IN which direction (toward or away from the replication fork) are DNA bases added during
replication on
i.
The leading strand
ii.
The lagging strand
11. Notice that both sides of the DNA molecule are utilized as templates to create new strands of
DNA. This is called semiconservative replication. Each new double stranded DNA contains one
original strand of DNA, and a new strand.
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INTRO TO THE STRUCTURE OF DNA
Name ______________________
12. Look at the replication fork you have created. As you add bases, maintain a replication fork, until
the strand is completed.
13. Now watch http://www.hhmi.org/biointeractive/dna-replication-schematic
a. This provides a basic picture of DNA replication
14. http://www.hhmi.org/biointeractive/dna-replication-basic-detail to see replication with all the
enzymes in place.
15. Finally, look at the video on Chargaff’s Rule (Ratio). What is this video trying to tell you?
http://bcove.me/jajuxtu4
If 30% of an organisms DNA was made of Adenine bases, what would be the percentages of the
other three bases. Explain why,
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