Download DNA Replication

Part One: Exploratory Questions
1. What are two examples of nucleic acids?
2. What builds/makes nucleic acids?
3. Where can we find nucleic acids in living things?
4. What is the function of nucleic acids to living things?
5. Does a strawberry contain all four macromolecules? Explain.
Part Two: DNA Extraction
1. Have one group member retrieve the materials from the front table.
2. Put the strawberry in the plastic bag and squeeze out all the extra
air before sealing tightly.
3. Mash the fruit with your hands for about two minutes until it is
mushy.
4. Add a squirt of soapy water and a pinch of meat tenderizer to the
fruit mush in the bag. Squeeze out the air and seal the bag
again.
5. Mash the mixture inside the bag for another minute.
6. Place a double layer of cheesecloth inside the funnel and set the
funnel on top of the test tube.
7. Pour the fruit mixture from the bag into the funnel. Let it drop
through the cheesecloth until there is no liquid left.
8. Throw away the cheesecloth and the fruit pulp inside it.
9. Tilt the test tube and very slowly, using the pipette, squeeze the
alcohol down the side. The alcohol will form a layer on top of the
fruit juice. Do not let the alcohol mix with the fruit juice!
10. Gently set your tube in the test tube rack to sit for 10 minutes.
11. While you are waiting, draw what you see in the test tube below.
Identify and label all layers.
12. After 10 minutes, Dip a skewer into the tube where the alcohol
and fruit layers meet.
13. Gently twist the skewer and try to catch some DNA (the white
precipitate) on the end of it.
14. Lift the white precipitate (DNA) out of the tube. Discuss: What
does it look like? What does it feel like? Is it easy to grab? What
color is it?
Part Three:Nucleotides & Complementary Base Pairs
The DNA you extracted from the strawberry was not a single DNA molecule, but long
ropes of thousands of molecules twisted together. Now we will look at what DNA
looks like at the molecular level, and what is inside each DNA molecule.
Go to the following website:
http://learn.genetics.utah.edu/content/molecules/builddna/
1. Click on ‘BUILD DNA’ and practice matching base pairs.
2. What does a cell need to do before it divides?
_____________________________________________________
3. How long does it take the ‘molecular machines’ inside of your cells to copy the
genetic information?
_____________________________________________________
4. True or False? DNA replication begins at a single location along each
chromosome.
_____________________________________________________
5. How many nucleotides per second are copied after the strands have been
separated?
_____________________________________________________
Scroll down to Complementary Base Pairing
6. What are the complementary base pairs for DNA?
______ pairs with ______
and
______ pairs with______
7. What type of bonds form between complementary bases?
__________________________________________
8. Why is complementary base pairing important for DNA replication?
___________________________________________
9. Fill in the blanks in on the diagram.
Go to the following website:
http://learn.genetics.utah.edu/content/cells/scale/
10. Put the following 10 items in order from largest to smallest:
___ Baker’s Yeast
___ Sesame seed
___ Red Blood Cell
___ Water Molecule
___ Ribosome
___ Adenine (A)
___ Hemoglobin
___ Human Sperm
___ Human Egg
___ Glucose
Part Four: DNA Replication
The process of making a copy of DNA is called DNA replication. The process can be
broken down into three steps.
Step 1: Before replication can begin, the double helix must unwind. This is
accomplished by enzymes called DNA helicases, which open up the double helix by
breaking the hydrogen bonds that link the complementary nitrogenous bases. Once
the two strands of DNA are separated, additional proteins attach to each strand,
holding them apart and preventing them from twisting back into their double-helical
shape. The two areas on either end of the DNA where the double helix separates are
called replication forks because of their Y shape.
Step 2: At the replication fork, enzymes known as DNA polymerases move along
each of the DNA strands, adding nucleotides to the exposed nitrogenous bases
according to the base-pairing rules.
Step 3: The process of DNA replication produces two DNA molecules, each
composed of a new and an original strand. The nucleotide sequences in both of these
DNA molecules are identical to each other and to the original DNA molecule.
1. What is replication?
__________________________________________________________
2. Where does replication occur?
__________________________________________________________
3. What must occur before replication can begin?
__________________________________________________________
4. The figure below shows DNA replicating. In the space provided, describe what is occurring
at each lettered section of the figure.
Part A
Part B
____5. DNA helicases and DNA polymerases are alike in that both are
a. nucleotides.
c. enzymes.
b. nitrogenous bases.
d. Both (a) and (b)
Part C
Part Five:Protein Synthesis
(DNA→RNA→AminoAcid→Protein)
Your DNA, or deoxyribonucleic acid, contains the genes that
determine who you are. This organic molecule controls your
characteristics because DNA contains instructions for all the
proteins your body makes. Proteins, in turn, determine the
structure and function of all your cells. What determines a
protein’s structure? It begins with the sequence of amino
acids that make up the protein. Instructions for making
proteins with the correct sequence of amino acids are
encoded in DNA.
Go to the following website:
http://learn.genetics.utah.edu/content/begin/dna/transcribe/
Complete each step as instructed, and then show
Mrs. Ritter your final protein and ask her initial in
the box.
Part Six: Problem Solving
Analyzing Peptide Chains
Huntington’s disease (HD) is a genetic disorder of the central nervous system with symptoms usually
appearing in adults within the third or fourth decade of life, although symptoms can occur in individuals
younger or older than this. Within the same family, the symptoms vary both in their rate of progression
and in the age of onset. Symptoms may include involuntary movements and loss of motor control. In
addition, personality changes may occur, with loss of memory and decreased mental capacity. Symptoms
in individuals, as well as confirmation of diagnosis in other family members, are used to determine the
diagnosis. Recently, scientists have found an association between HD and the repeat of the DNA
sequence, CAG (cytosine-adenine-guanine), on chromosome 4. Scientists have noted between 40-100
repeats in some patients. Suppose you have the ability to analyze peptide chains (chains of amino
acids)…
Below are samples from three people, explain how could you determine which applicant may have numerous CAG repeats.
Applicant 1
Applicant 2
Applicant 3
Glutamine-Serine- Proline- Valine- Isoleucine- Glutamine- Glutamine- Glutamine- Glutamine- Serine
Glutamine- Serine- Proline- Valine- Isoleucine- Isoleucine- Isoleucine- Isoleucine- Isoleucine- Serine
Glutamine- Serine- Proline- Valine- Isoleucine- Valine- Valine- Valine- Valine- Valine- Serine
Which, if any, is most likely to develop HD?
Part Six: Problem Solving
Reading DNA Markers
Sample 1-Normal Cytochrome C
A
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T
G
C
DNA
CGA
RNA
GCU
Amino Acid
Alanine (Ala)
Instructions
1. On the left is a gel that was used to separate
DNA into individual bases.
2. Read the DNA gel and write the
corresponding RNA triplet in the RNA
column.
Remember – RNA does not have (T)!
3. Using a codon chart, write the corresponding
amino acid in the next column.
4. Complete the transcription and translation
of the entire gel.
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