MODELING GENETIC ENGINEERING
An understanding of the basis of inheritance has led to
a new form of applied genetics
use of genetics for practical
purposes. For example, it can
ed to identify genes f
or specific traits or transfer
genes for a specific trait from one organism
to another organism.
Gene transfer was first implemented in the field of
medicine in the production of
1912 to the early 1990s, diabetic pa
needed to obtain insulin from
pigs or cows in an effort
control their blood suga
r. Although pig or cow insulin
worked effectively on most patients, some
rgic reactions. Gene transfer
allowed the mass production of human insulin
potential side effects.
HOW DOES IT WORK?
Use handout 3 to create a model
The plasmid is a ring of DNA
found in bacteria
in addition to their main chromosome.
Cut the plasmid strips along the dotted lines.
fle the strips and tape them together to form a single long strip.
The letters should all be in the same direction when the strips are taped.
Tape the two ends together to form a circular plasmid from a bacterium.
Use handout 4 to cr
Cut out the base sequence strips along the dotted lines.
Tape the strips together in numeric order to form a single long strip.
Note that the shaded area is the insulin gene.
able to cut open the plasmid in one
Restriction enzymes are like chemical scissors that can recognize very specific
. Look for example, at the DNA sequence below. The restriction enzyme recognizes
sequence CAATT on both chains of DNA. In one chain, the sequence runs
from left to right;
on the complementary chain, the sequence runs from right to left.
Use handout 5 to select the restriction enzyme:
Cut out the restrictio
n enzyme cards.
The enzyme cards illustrate a short DNA sequence that each enzyme can cut.
Compare the base sequence on each enzyme card with the base sequence of the plasmid.
Some restriction enzymes may be able to cut open the plasm
id in multiple locations while
others may not be able to cut open the plasmid at all. You are in search of an enzyme
able to cut the plasm
id sequence once and only once!
List the enzymes
able to cut open the plasmid
in only one location
Mark the cutting location of the restriction enzymes on the plasmid.
able to cut open the
Compare the restriction enzymes
able to cut open the plasm
against the human DNA
Find an enzyme that will
make two cuts in the DNA sequence:
one just above and one just below the shaded insulin gene.
Mark the two cutting locations of the restriction enzyme on
the human DNA sequence.
tion enzyme is
able to cut
open the DNA in all three locations:
below the insulin gene,
above the insulin gene
the plasmid? ______
Create “sticky ends
Sticky ends are the “tails” created when restriction
enzymes cut open DNA.
Select the one
enzyme able to cut both the plasmid and human DNA sequences.
Cut open the circular plasmid at the location you marked in pencil.
Cut out the insulin gene at the 2 locations you marked.
Modify the plasmid.
At this point both your plasmid DNA and human DNA have “sticky ends.”
Insert the human DNA sequence containing the insulin gene into the plasmid DNA.
Tape the sticky ends of the insulin gene
onto the sticky ends of the
Neatly fold and staple your modified plasmid to this handout
NOW WHAT HAPPENS?
The modified plasmid is inserted in a bacterium.
Note that the plasmid
now carries the
human insulin gene capable of p
The bacteria reproduce.
are able to
reproduce at a prodigious
Each of the bacteria
offspring can now produce insulin. The remarkable
result is the ability
to produce insulin en masse for diabetic patients.
What is a plasmid?
What is a restriction enzyme?
it important t
o find a restriction
enzyme that will cut the plasmid only once?
Why is it important to cut the DNA strand as close to the insulin gene as possible?
Use the Internet to find
of genetic engineering
other than the production of insulin.
Print your Internet source and staple it to this activity