Name: Xyrelle L.
Espiel
Grade & Section: 11- STEM Marie Curie
Biology
DNA Replication: Paper Clip Activity
Quick Review:
Each DNA molecule has a unique structure that makes it different from other DNA molecules (or genes).
This difference occurs because the sequence of A, T, C, and G vary from one molecule, or gene, to another.
What You Need to Know About DNA Replication:
To “replicate” means to produce a copy. DNA is the only known molecule that can make a copy of itself.
DNA is able to make an exact replica of itself because of the base pairing (complementary) characteristics stressed earlier
(A with T; C with G).
When DNA makes a duplicate molecule of itself, the two strands unwind.
After the two strands have pulled apart, new bases (A, T, C, & G) as well as new sugar and phosphate units come into place
according to the base pairing rules.
A comes in opposite of T, and C is opposite of G.
When this occurs, two identical DNA molecules are created.
Overview:
You will be making a short sequence of a human gene that controls the body’s production of the growth hormone, which cases growth
during childhood and adolescence. Genetic engineers call this gene the hGH (human Growth Hormone) gene.
For this activity, each pair of students will need the following:
14 Pink clips = Adenine(A)
14 Orange clips =Thymine (T)
9 Violet clips = Cytosine(C)
9 Green clips =Guanine (G)
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STEP ONE:
Use the colored paper clips, according to the key above, and construct the top strand of the hGH gene according to the diagram of the
gene below. Link the ten appropriate colored clips for the top strand shown below.
STEP TWO:
Now, construct the bottom strand of the hGH gene by linking ten more clips into a chain according to the strand you filled in above. The
entire sequence of this gene is known. Your DNA model should resemble the following:
STEP THREE:
Set the two chains side-by-side as shown in the drawing above so that A bonds with T, and C bonds with G. You now have a model of
the hGH gene (the first ten bases only).
Compare the two chains with each other side-by-side to verify that C bonds with G, and A bonds with T. When this gene replicates in
the nucleus of a cell, the double-strand begins to separate to one end. As it separates, new nucleotide bases are moved into place by
enzymes, which form the beginning of two new identical molecules. These A, T, C, and G bases are present in the nucleus of each cell
and come from food molecules. When these new bases are brought into place, the A bonds with T, and the C bonds with G.
STEP FOUR:
Open your hGH DNA molecule as shown below:
STEP FIVE:
Now use the other (unused) clips to create the beginning of two new strands. REMEMBER A with T, and C with G. Connect the clips as
follows:
STEP SIX:
Continue separating the strands and bring in the appropriate new bases (clips) to create two complete new double stranded hGH gene
molecules. REMEMBER that A is complementary to T, and C is complementary to G. **you should have 6 clips left. Save them for
later.
Questions:
1. Examine the two double-stranded DNA molecules you created. Are they identical or different in any way?
The two double-stranded DNA are identical it is because the bases are complementary paired which results to two identical
strands of DNA molecule.
2. You now have two copies of a segment of the hGH gene on you table. During periods of growth and cell division, the
chromosomes (made up of genes) must divide. What features about DNA replication causes each new DNA molecule to be
exactly like the original?
It is the complementary base pairing feature of DNA that causes each new DNA molecule to be exactly like the original.
Adenine only associates with Thymine. Guanine only associates with Cytosine. Therefore, the sequence of the base pairs are
identical in the 5’ to 3’ direction.
3. When this mutated DnA molecule replicates, will the resulting new DNA be similar or different from the hGH gene? Explain.
When this mutated DnA molecule replicates, the result of the new DNA will be different from the hGH gene because it has
been modified by the mutation and mutation is located under the strand being replicated.
4. Explain how mutations can occur in cells and how this might affect the new organism with the mutation.
Mutations occur in cells when the DNA is replicating. Sometimes gene mutation prevents one or more of the proteins from
working properly. By changing a gene’s instruction for making a protein, the gene mutation may cause a malfunction to the
protein of the organism or to be gone entirely. When this mutation alters the protein, it can disrupt a normal development or
cause a medical condition or a genetic disorder.
5. Draw the structures of the new double-stranded mutated gene you created by using the letters A, T,C, and G in a manner similar
to that shown earlier.
Generalization
In our body while our DNA is replicating, mutation also is ongoing. It is not all the time that this mutation can cause good
effects but also it can also cause genetic disorder to an organism. In some cases, this gene mutation prevents an embryo from
surviving until birth because this mutation has serious effects it is not compatible for life.
Reference:
http://www.tiemanbiology.com/uploads/6/3/2/6323843/dna_replication_clip_activity.pdf.
