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NAME _________________________
THE LIVING ENVIRONMENT
LAB
AVERILL PARK HS
DNA & RNA Model Lab Activity
DNA REPLICATION, TRANSCRIPTION & TRANSLATION
(Modified from Joslin/Boulay, 2007)
INTRODUCTION
Deoxyribonucleic acid (DNA) is a complex molecule found in all living organisms. It is the
hereditary material that makes up genes (which are found on our chromosomes).
An understanding of the molecular structure of this molecule has revolutionized the focus of
research throughout the world in many disciplines - including drug production & therapy,
vaccine production, diagnostic tools for diseases, agriculture, food processing, cloning and
artificial reproductive technologies.
Scientists now have an understanding of how chromosomes replicate prior to cell division and
transfer their genetic information to every new cell. Scientists also recognize how the DNA
molecule "stores" the hereditary information in the genes, and how this information is used to
synthesize proteins with the help of RNA.
In this investigation you will use paper models to:
 Construct a portion of a DNA molecule
 Replicate the DNA molecule
 Transcribe & translate the DNA model
MATERIALS
 One envelope of DNA & RNA nucleotides
METHODS, RESULTS & DISCUSSION
Part 1: Structure of a DNA molecule
The paper models represent DNA & RNA nucleotides.
 Take the models out of the envelope and sort them into 2 piles  One pile of DNA
nucleotides & one pile of RNA nucleotides
 Sort the DNA nucleotides into 4 separate piles according to their nitrogenous base and
count them. Check the front of the envelope to be sure they are all there. Let your
teacher know if you are missing any nucleotides.
 When the DNA molecule is "unwound" from its chromosome form, it has a double helix
shape (very similar to a ladder). Each SIDE of the ladder consists of a single strand of
nucleotides. You are now ready to build a portion of a DNA molecule. Build the molecule in
between your partner and yourself so you can both view the model.
 Connect 6 DNA nucleotides together to form ONE row in the following sequence
(from TOP to BOTTOM):






Cytosine (C) nucleotide
Thymine (T) nucleotide
Guanine (G) nucleotide
Adenine (A) nucleotide
Guanine (G) nucleotide
Cytosine (C) nucleotide
 Complete the RIGHT side of the ladder by matching complementary bases to the exposed
nucleotides (using the rules for base-pairings).
 Refer to your DNA model & your notes in order to answer the following questions:
1. Draw a single DNA nucleotide & LABEL each part.
2. Which 2 molecules alternate to form the "backbone" (upright sides) of the DNA ladder?
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3. What holds the nitrogenous bases together in each rung of the ladder?
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4. Is the order of the nitrogenous bases EXACTLY the same on each strand? Explain.
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5. Only two combinations of complementary base pairing exist in the DNA molecule. List
these two combinations.
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6. If 18 guanine (G) bases appear in a DNA model, how many cytosine (C) bases would you
expect there to be?
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Part 2: DNA/chromosome Replication
Your DNA model represents only a TINY length of the DNA portion of a gene/chromosome.
A single gene may have thousands of nucleotides while a chromosome may have hundreds of
thousands of nucleotides. Although your model is only a tiny portion of the molecule, its
replication is the same as that of an entire gene or chromosome prior to cell division.
 "Unzip" (split apart) your DNA molecule along the weak hydrogen bonds between the
nitrogenous bases and separate the model into 2 halves.
 Using the LEFT half of your model as a template, add NEW nucleotides to form a new
RIGHT side.
 Build a second DNA model by adding the complementary nucleotides to the RIGHT half of
the original model.
7. Now compare the two separate DNA models resulting from your DNA replication. Is the
ORDER of nitrogenous bases on each model the same or different?
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8. Why is complementary base pairing so important during chromosome replication (i.e., what
does it ensure)?
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Part 3: Transcription of DNa to rna
DNA has another function in cells other than to replicate itself. It STORES the
information needed to make all the proteins in a cell (and in the organism). This information
is stored in the sequence of nucleotides along the DNA strand. Each gene has the "code"
(directions) to produce a specific polypeptide (protein) chain.
 To transcribe an RNA molecule from DNA, unzip the double-stranded DNA molecule.
 Then, using the RIGHT side of the DNA molecule as a template, match the RNA
nucleotides that are complementary to the DNA nucleotides.
9. What is this process of "converting" the DNA code called?
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10. Where in the cell does this process occur?
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11. Where will the mRNA molecule go once it's
formed?
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 After the mRNA strand is formed, the
DNA molecule zips itself back up. To
illustrate this with your model, remove the
RNA nucleotides from the DNA template
and close up the DNA molecule. Keep your
RNA model intact.
Part 4: Translation of Codons
 Observe the RNA molecule that was just transcribed from the DNA molecule.
12. How many nucleotides are present in the mRNA molecule model? _____
13. How many codons does this create? _____
14. Use the genetic code to complete the following:
 DNA code (RIGHT side)
___ ___ ___ ___ ___ ___
 mRNA codon
___ ___ ___ ___ ___ ___
 Polypeptide chain
__________ - __________ etc…
15. Now assume the original DNA code (right side) was mutated by UV light and changed to
GAC TTG. Complete the following:
 Mutated DNA code
___ ___ ___ ___ ___ ___
 mRNA codon
___ ___ ___ ___ ___ ___
 Polypeptide chain
__________ - __________ etc…
16. Compare the two dipeptides produced by the NORMAL and MUTATED codes.
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17. How might a mutation in your DNA affect the synthesis of proteins in your body?
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18. Name a few environmental factors (mutagens/carcinogens) that could mutate your DNA.
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19. Using the chart below, compare the structure of DNA with that of RNA. Include at least
two similarities & two differences.
COMPARISON
DNA
RNA
SIMILARITIES
DIFFERENCES
20. Using the chart below, compare the process of DNA replication with the process of
transcription. Include at least two similarities & two differences.
COMPARISON
SIMILARITIES
DIFFERENCES
DNA Replication
Transcription