Name___________________________
Prelab Questions: What is the structure of DNA (Chapter 10 pg. 196-201)
Use Chapter 10-2 to answer the following questions: This section talks about the structure of DNA
1.
Is type of macromolecule is DNA ( carbohydrate, lipid, protein or nucleic acid)? . What are the
monomers of this macromolecule called?
2. What are the three basic parts of this monomer. Draw the monomer
3.
The DNA double helix is similar to a spiral stair case (helical). But why is it called a double helix?
4. What parts of the monomer are joined together with covalent bonds?
5. What is joined together with hydrogen bonds? What is the purpose of the hydrogen bonds?
6. There are four nitrogenous bases. Name the bases.
7.
Bio A
Define complementary base pair.
8.
Draw a strand of DNA (in a ladder form) that has the following sequence on one side (yes that
means you need to “come up with” the other side : ) . Create it so that the first six bases (on
the left) have “opened” at the hydrogen bonds (so it should look like a Y that is sideways.
TAC GCA TTC AAA TCA GGT CCG
9. What are the three major steps in replication identified in the book? Name the step, the
enzyme involved and the key events.
10. Prokaryotes have one circular chromosomes, while eukaryotic cells have MANY long noncircular pieces of DNA. How is the efficiency of copying increased in eukaryotes (ie, how do we
make the time to replicate all that DNA shorter?)
11. How might errors in DNA replication occur? What do we call these errors?
Bio A
DNA Modeling Activity
Begin by checking your bag for the following components:
Pieces
What they represent
3 small blue straws
Adenine base (A)
3 small red straws
Thymine base (T)
3 small green straws
Guanine Base (G)
3 small grey straws
Cytosine Base (C)
12 Black three prong
Deoxyribose sugar
12 Red two prong
Phosphate group
6 White two prong
Hydrogen bond
24 yellow short straws
Phosphodiester (covalent) bond
1 long light green straw (6 inches)
Support for helix
3-extra “longer” pieces (various colors) straws
Support stand
1 black or grey four pronged base
Support stand
Objective: To build a 3D helical model of DNA by linking together nucleotides in the proper
arrangement. READ EACH QUESTION COMPLETELY BEFORE ASSEMBLING YOUR MODELS.
Procedure:
1. Begin by building 12 separate nucleotides. Use your book and the “parts list” above to determine
how to make your nucleotide. You will need a bond (yellow straw) to join the phosphate group to the
sugar. The based (small straws) attach directly to the sugar. Make sure each nucleotide has a Sugar, a
Phosphate and a Base and that the pieces are linked together using the proper bond.
Show me your 12 nucleotides BEFORE linking them and I will sign here ______________
2. When you have completed the building the 12 nucleotides, use 6 of them to build a SINGLE chain
with the following nucleotide sequence: A-G-A-C-T-
C
3. Once you have that chain built, imagine the second side is being assembled nucleotide-by-nucleotide.
Add the correct nucleotide (in sequence) to form the complementary pair (you will need a”hydrogen
bond” between each of the complementary pairs. Add 2 nucleotides, then join the nucleotides together
with a covalent bond (yellow straw). Make sure you are pairing up complementary bases! Also make
sure that the correct bond is between bases
4. Once your DNA ladder is complete, twist all the center hydrogen bonds so the center holes face
down. Thread the LONG light green straw through all those center holes.
5. Show me your completed model and I will sign here _______________________.
Bio A
DNA REPLICATION ACTIVITY
Once you have been “signed off” to create, you replicate on of the DNA models that your lab group
created.
1. Use the diagram at the bottom of the page to record your DNA sequence (both strands), by
writing down the first letter of each base, with its complementary base (choose only one of the
models you created at your table)
2. How many nucleotide pairs do you have in your DNA model? _____________
3. How many chains of nucleotides are present? ________________
4. Disconnect the nucleotides on the 2nd DNA model, so that you have 12 bases to use for
replication. Open one end of your remaining DNA model (one or two base at a time to each side
on the original model by removing two hydrogen bonds (pretend you are helicase) Then add
complementary nucleotides to each side (bond nucleotides on each side together using a
covalent bond). Make sure the model remains together at the P-S backbone and that the
remaining four hydrogen bonds stay intact
________________ Check off point for replication fork. Be able to explain to Mrs. Landa how
replication would continue and what the end products would be.
5. Continue (one hydrogen bond at a time) until you have two copies that look exactly like the
original. When you have two DNA strands, identify (to each other) the phosphate-sugar
backbone , covalent bonds, hydrogen bonds. Label
these on the diagram below.
6. Demonstrate the actions of helicase and DNA
polymerase to your lab partner. Describe each
function below:
a. Helicase function:
b. DNA polymerase function:
7. You have just completed semi-conservative
replication. What does this term mean?
Bio A
ASSESSMENT
Written Activity: Write a paragraph describing replication using the following terms. Put this in a logical
sequence. You must use complete sentences. UNDERLINE EACH TERM and put the number of the word
underneath the underline
1. Double helix
2. Nucleotide
3. complementary
base
4. template
5. Helicase
6. DNA Polymerase
Bio A
7. Semiconservative
replication
8. Sequence
9. Phosphate
10. Deoxyribose
Sugar
11.
12.
13.
14.
15.
Base
Thymine
Cytosine
Guanine
Adenine.