MODELING GENETIC ENGINEERING

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11 Δεκ 2012 (πριν από 4 χρόνια και 8 μήνες)

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MODELING GENETIC ENGINEERING


INTRODUCTION



An understanding of the basis of inheritance has led to
a new form of applied genetics
called genetic

engineering.
Genetic engineering

is the

use of genetics for practical
purposes. For example, it can

be us
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
insulin. From

1912 to the early 1990s, diabetic pa
tients

needed to obtain insulin from
pigs or cows in an effort

to

control their blood suga
r. Although pig or cow insulin
worked effectively on most patients, some

suffered alle
rgic reactions. Gene transfer
allowed the mass production of human insulin
without

potential side effects.


HOW DOES IT WORK?


STEP 1

Use handout 3 to create a model
plasmid
.




The plasmid is a ring of DNA

found in bacteria
in addition to their main chromosome.





1.

Cut the plasmid strips along the dotted lines.




2.

Shuf
fle the strips and tape them together to form a single long strip.




3.

The letters should all be in the same direction when the strips are taped.




4.

Tape the two ends together to form a circular plasmid from a bacterium.




STEP 2

Use handout 4 to cr
eate
a

human

DNA sequence
.





1.

Cut out the base sequence strips along the dotted lines.




2.

Tape the strips together in numeric order to form a single long strip.




3.

Note that the shaded area is the insulin gene.






STEP 3

Select a
restriction en
zyme

able to cut open the plasmid in one
specific
location
.






Restriction enzymes are like chemical scissors that can recognize very specific

sections of




DNA
. Look for example, at the DNA sequence below. The restriction enzyme recognizes




the
nucleotide
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:





1.

Cut out the restrictio
n enzyme cards.




2.

The enzyme cards illustrate a short DNA sequence that each enzyme can cut.




3.

Compare the base sequence on each enzyme card with the base sequence of the plasmid.




4.

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!





5.

List the enzymes

able to cut open the plasmid

in only one location
:
_____
_
________
__.




6.

Mark the cutting location of the restriction enzymes on the plasmid.



STEP
4

Select a
restriction enzyme

able to cut open the
human DNA

in
two

specific location
s
.






1.

Compare the restriction enzymes
able to cut open the plasm
id
against the human DNA
.




2.

Find an enzyme that will
also
make two cuts in the DNA sequence:





one just above and one just below the shaded insulin gene.




3.

Mark the two cutting locations of the restriction enzyme on
the human DNA sequence.






Which restric
tion enzyme is
uniquely
able to cut
open the DNA in all three locations:





below the insulin gene,
above the insulin gene
, and
also

the plasmid? ______



STEP 5

Create “sticky ends
.”




Sticky ends are the “tails” created when restriction
enzymes cut open DNA.





1.

Select the one
unique
enzyme able to cut both the plasmid and human DNA sequences.




2.

Cut open the circular plasmid at the location you marked in pencil.




3.

Cut out the insulin gene at the 2 locations you marked.























STEP 6

Modify the plasmid.





1.

At this point both your plasmid DNA and human DNA have “sticky ends.”




2.

Insert the human DNA sequence containing the insulin gene into the plasmid DNA.




3.

Tape the sticky ends of the insulin gene

onto the sticky ends of the

plasmid.




4.

Neatly fold and staple your modified plasmid to this handout
.

plasmid DNA

human DNA
containing the
insulin gene

NOW WHAT HAPPENS?



1.

The modified plasmid is inserted in a bacterium.

Note that the plasmid





now carries the

human insulin gene capable of p
roducing insulin.



2.

The bacteria reproduce.

B
acteria
are able to

reproduce at a prodigious

rate.




Each of the bacteria
offspring can now produce insulin. The remarkable



result is the ability

to produce insulin en masse for diabetic patients.





REVIEW


1.

What is a plasmid?



______________________________________________________________________________



2.

What is a restriction enzyme?



______________________________________________________________________________



3
.

Why
is
it important t
o find a restriction

enzyme that will cut the plasmid only once?



______________________________________________________________________________



4
.

Why is it important to cut the DNA strand as close to the insulin gene as possible?



___________________
___________________________________________________________



5.

Use the Internet to find
an application

of genetic engineering

other than the production of insulin.



Print your Internet source and staple it to this activity
.



___________________________
___________________________________________________



______________________________________________________________________________