Activity:
Genetic Engineering
Name ______________________________
INTRODUCTION:
People with diabetes require extra insulin to live a normal
life. In the past, the insulin they need has been obtained
from cows and pigs. This type of insulin is very expensive
and often can carry proteins which cause allergic
reactions. Recently, scientists have perfected a method to
combine the human gene for insulin with bacterial
DNA. This type of DNA is called recombinant DNA. Once
the gene for insulin is combined with the bacterial DNA,
the bacteria can then produce human insulin. This
insulin is cheaper to produce and is relatively free of
allergens (proteins which may cause allergic reactions).
RECOMBINANT DNA PROCESS:
Bacteria often contain small circular pieces of DNA called plasmids in addition to their regular
DNA. These plasmids frequently carry genes for antibiotic resistance. They are also easily
separated from bacteria and easily reabsorbed into bacteria. Because of these properties, scientists
use plasmids as a vector (carrier) for the insulin gene. Once the plasmids (includes DNA for insulin) are
absorbed into bacterial DNA, “the code” will be translated into products by the bacteria. The bacteria
which absorbed the plasmid are identified by their altered resistance to antibiotics and grown in
large quantities. The insulin they produce is purified and marketed.
MARKETING:
This method of genetic recombination is a window to the future. Many genetically engineered
organisms have been created so far such as oil slick digesting bacteria and bacteria which confer
insect resistance to their plant hosts. The future of recombinant DNA also holds the promise of
correcting genetic disorders in humans through gene therapy (Insertion of normal genes to overcome
detrimental products or lack or product from a mutated gene). The Human Genome Project has paved
the way for this type of gene therapy because it has sequenced the entire human DNA.
Purpose
In this activity, you will construct a simple model of the process of genetic recombination (gene transfer)
which demonstrates the insertion of an insulin gene into a bacterial plasmid.
Materials




Activity packet (including DNA sheet)
Scissors
Tape
Colored Pencils
Method
1. Color the gene for insulin, the gene for tetracycline resistance, and the gene for ampicillin
resistance using different colors. These are the shaded portions of the DNA sequence page.
Make a note of which color was used for which gene.

Insulin gene:

Tetracycline resistance: __________________

Ampicillin resistance:
__________________
__________________
2. Cut out the DNA strip for each type of DNA. Assemble the plasmid DNA (ampicillin strip) into
a circle by taping the ends together. Leave the insulin gene flat.
3. Use the template below to draw a diagram of the circular plasmid DNA not including base pairs.
Label the areas of antibiotic resistance using same colors as in step 1.
4. Restriction enzymes are used to cut DNA at specific, known points in the base pair sequence.
These enzymes don't just chop the DNA molecule in half, they cut into one strand and then cut
between base pairs before cutting through the other strand of the DNA molecule. This results in
"sticky" ends on the cut edges of the DNA. The enzyme used to cut open the plasmid DNA is
also used to cut out the insulin gene from a segment of human DNA. Look at the model of the
restriction enzyme cut on the DNA sequence page. Notice the pattern that it cuts.
5. Cut your DNA at the base sequence that matches the restriction enzyme site. Be sure to cut
exactly as shown on restriction enzyme model each time. You will need to make a cut on each
side of the insulin gene and just one cut to open the plasmid. You should have "sticky" ends on
both the plasmid and the human DNA.
6. Since the sticky ends are matched up between the insulin gene and the plasmid DNA, a ligase
enzyme joins the pieces. Insert the insulin gene into the plasmid by matching up sticky ends
and taping the pieces together. You now have recombinant DNA!!
7. Draw a diagram of new recombinant plasmid. Indicate insulin gene placement. Use the color
scheme established in step 1.
Activity:
Genetic Engineering
Name ______________________________
Analysis Questions
1. What two types of enzymes are required to make recombinant DNA?
2. You used scissors and tape in this lab.
a. Which enzyme was represented by the action of the scissors to cut open plasmid and
cut insulin gene from DNA strip?
b. Which enzyme was represented by taping together the "sticky" ends?
3. Why do scientists use the same enzyme to remove the insulin AND cut the plasmid open?
4. When you cut the plasmid DNA with your "enzyme" did you cut into either of the gene for
antibiotic resistance? If so, which one(s)?
5. Humans are very different from bacteria. Why do you think it is possible to combine their DNA
and have bacteria successfully manufacture human protein?
Ampicillin
resistance gene
Tetracycline resistance gene
DNA Sequence
T
A
C
T
T
G
G
A
T
G
A
T
C
C
A
C
T
G
PLASMID
Human Insulin Gene
A
T
G
A
A
C
C
T
A
C
T
A
G
G
T
G
A
C
HUMAN DNA
INSULIN GENE
G
C
T
T
G
G
G
T
A
G
C
G
T
T
G
G
C
A
RESTRICTION ENZYMES
cut along the solid line anywhere the
sequence is found (either direction)
C
G
A
A
C
C
C
A
T
C
G
C
A
A
C
C
G
T
T A
T A
G C
G C