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DNA Replication Candy Model
Biology I
Name:______________________
Period:__________________
DNA Replication Candy Model
Purpose: To observe the structure of DNA, complimentary base pairing and the process of
DNA replication.
Materials:
2 red twizzlers
2 black twizzlers
Colored marshmallows
Toothpicks
Scissors
Background: DNA (deoxyribonucleic acid) is found in the chromosomes of all living things.
The chromosomes (located in the cell’s nucleus) contain genetic information in long sequences
of DNA (DNA chains can be millions of nucleic acids long). DNA provides a set of instructions
on how to build the proteins in every living organism, what proteins are needed to create the
organism, and in which sequence amino acids are needed in order to build all of the different
proteins required for the organism’s growth.
Structure: All DNA (in humans, snakes, frogs, birds, turtles, insects, etc.) is composed of three
parts: a five carbon sugar called deoxyribose, a phosphate group, and a nitrogen-containing base
(there are 4 potential bases in DNA: adenine, guanine, cytosine, and thymine). The three part
components of DNA make up nucleotides. Nucleotide chains are formed as the phosphate group
of one nucleotide attaches to the sugar of the following nucleotide. The structure of DNA is a
double helix similar to the shape of a “ladder” that has been twisted. The phosphate/sugar
attachments are on the outside “uprights” of the ladder, while the attached bases, between the
two nucleotide strands, can be considered the “rungs” of the ladder. Two strands of sugar and
phosphate backbone are twisted and connected to alternating bases.
Complementary Base Pairing: The alternating bases (the “rungs” of the ladder) pair together
between the two DNA strands in complementary pairs. Adenine always pairs with thymine,
while cytosine always pairs with guanine. Therefore, in the double helix structure, one DNA
strand is matched to complementary bases of the other strand.
Activity:
Step 1: Assemble one side of the DNA Model
Place 12 toothpicks evenly spaced apart, into the side of a red licorice stick.
Using the chart below put a marshmallow onto the end of the toothpick in the order of
sequence
CTCGTAGAGATC
A = Adenine
T = Thymine
C = Cytosine
G = Guanine
=
=
=
=
pink marshmallow
orange marshmallow
green marshmallow
yellow marshmallow
DNA Replication Candy Model
Biology I
Name:______________________
Period:__________________
What does the red licorice stick represent? ________________________________
Step 2: Match the Nitrogen Base Pairs
Match the nitrogen base pairs with the corresponding marshmallow
base pairs and place onto the end of the toothpick.
Adenine pairs with ______________________.
Cytosine pairs with ______________________.
Step 3: Complete the DNA model.
After all base pairs have been added, place the licorice back bone parallel to the other backbone.
Step 4: Twist the DNA model.
By twisting the DNA model, the
______________ ______________ shape is shown.
Step 5: Zoom in to the DNA model.
The individual compounds that make up the DNA are known as _______________;
and are made of 3 portions: a nitrogenous base (represented by the
________________ in this lab), sugars and phosphate (represented by the
_______________ in this lab)
Step 6: Label the completed DNA model.
Place the DNA on a white sheet of paper. Label each part of the
DNA model by drawing a line and writing the corresponding
part on the paper.
Where is DNA found in the cell? ___________________
DNA Replication Candy Model
Biology I
Name:______________________
Period:__________________
Step 7: “Unzip” the model to begin the replication process.
Using a pair of scissors cut the middle of the toothpicks to
create separate strands of DNA.
What do the scissors represent? ___________________
Step 8: Create nucleotides.
Cut each piece of black twizzler into 12 pieces.
Place a toothpick into each piece of black twizzler.
Using the original strands of DNA and complimentary base pairing, place the correct
marshmallows onto the toothpicks of your new nucleotides.
Step 9: Place new nucleotides onto the original DNA strands.
Remove the broken toothpicks from the original strand. Take the marshmallows from the
broken toothpick and place it on the new toothpick (make sure to use complimentary base
pairing to match it correctly).
This step represents which enzyme? __________________________
Place the newly paired marshmallows and black twizzler piece onto the original strand.
Continue to do this until you have two copies of the original DNA.
What does DNA ligase do? _________________________________________________
Sometimes mistakes happen during replication. These mistakes are called mutations.
Have another student make double check your base pairing and sequence of your strands.
What enzyme does the student represent? _____________________
DO NOT DISPOSE OF MODEL UNTIL A
TEACHER HAS CHECKED IT!!!!
Step 10: Dispose of your model.
DNA Replication Candy Model
Biology I
Identifies structures/locations:
Hydrogen bonds, sugar-phosphate
backbone, nucleotides, nucleus
Exhibits Correct Base-Pairing
Enzymes are shown performing their
functions and labeled
Name:______________________
Period:__________________
Level 3:
Exceptional
Level 2:
Satisfactory
Level 1:
Unsatisfactory
Identifies all
structures/locations
correctly.
All base-pairings
are complete.
Identifies all but one
structure/location
correctly.
A few (no more than 3)
rungs may be
incorrectly paired.
One enzyme is labeled
or portrayed
incorrectly.
Identifies 2 or more
structures/locations
incorrectly.
More than 3 rungs are
incorrectly paired.
All enzymes are
portrayed and
labeled correctly.
More than one enzyme
is labeled or portrayed
incorrectly.
Questions:
1. How is the process of DNA Replication “semi-conservative”?
2. What are enzymes and what function do they serve?
3. What is a mutation? Why does the process of DNA replication create so few of them?