Biology Simulation Lab: Genetic Engineering Techniques

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

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Biology Simulation Lab: Genetic Engineering Techniques


In this activity, we’ll model some of the techniques used by scientists to manipulate DNA and
produce transgenic organisms.

Such techniques have revolutionized biology
, increased our
understanding of

life dramatically
,

and hold the promise of
future

treatments and cures for
many
disease
s
.

Answer all the
bold
-
typed
questions in Part 3 on the back of this sheet.



Part 1: Making Paper DNA

1.

Get 3 strips of
differently
colored paper

DNA templates
. The diff
erent colo
rs

represent

DNA
from three different species.

2.

On
one of
the strip
s
, w
rite
HindIII

at the top, then write
the
recognition

sequence

for the
enzyme

HindIII

in
two

places on the template

(see diagram below)
.

Don’t

write the
base
recognition sequence

at the ends

of the strip
, or
right

next to one another.

3.

Repeat the previous step on the other two strips for the enzymes

EcoRI

and
SmaI
.

4.

Use a highlighter or colored marker to trace the cutting path of the enzyme at both recognition
site
s

on
each of the t
hree paper DNA’s.

5.

Fill in all the other empty base sites on the DNA templates with random A’s, T’s, G’s and C’s.
Make sure that the bases are correctly paired!


Part 2:
Cutting DNA

with Restriction Enzymes

1.

Simulate the cutting action of the restriction en
zymes by
using scissors to cut

through all the
recognition sequences for each paper DNA.
Cut through the DNA on the paths you
traced in
step
5

of Part 1.

2.

There should be at least 2 cut sites on each strip, so you should have at least three DNA
fragments fo
r each of your original paper DNA molecules.


Part 3: Making Recombinant DNA

1.

Find a classmate to work with.

2.

Look at the fragments produced by the enzyme that produces “blunt ends” when it cuts the
DNA.

a)

Are the DNA molecules cut by this enzyme from the s
ame
species (same color
paper)?

b)

Would the fragments
from the same original strip be attracted to one another?

c)

Would
the
fr
agments be chemically attracted to one another?

3.

Compare the ends of the fragments from your DNA strips that were cut with
the two
diff
erent enzymes

that produce “sticky ends.”

a)

Do they have complementary “sticky ends?”

Would the
se

fragments form
hydrogen bonds with one another?

4.

Compare the ends of fragments from your DNA strips that were cut with the same enzyme that produce
“sticky ends.


a)

Are the DNA molecules cut by this enzyme from the same species (same color paper)?

b)

Would these fragments form hydrogen bonds with one another
regardless of whether the DNA
was from the same species or not?

5.

Find DNA fragments
from different species
with c
omplementary sticky ends
.

6.

Place the complementary sticky ends next to one another. Because these sequences are chemically attracted
t
o each other, if fragments like these were mixed together in the same test tube, some of them would stick to
each other jus
t like this.

7.

To make the connection between the two fragments permanent, and enzyme called DNA ligase is used. The
enzyme
forms covalent
bonds
between the ends of adjacent single
-
stranded DNA fragments. Simulate the
action of DNA ligase by
using two small
strips of clear tape to connect the backbones of the two DNA
fragments.

a)

If the fragments were not joined by DNA ligase, would they be likely to remain stuck together?
Explain.

8.

Show your teacher the recombinant DNA you just made.

HindIII


A AGCTT

TTCGA A


EcoRI


G AATTC

C
T
T
AA G



SmaI


GGG
C
CC

CCC GGG

-

A


T
-

-

G


C
-

-

C


G

-

-

T


A
-

-

A


T
-

-

A



T

-

-

A


T
-

-

G


C
-

-

C


G
-

-

T


A
-

-

T



A

-

-

G


C
-

-

A


T
-

-

G


C
-

-

C


G
-

-

T


A
-

-

A


T
-

-

G


C
-



Recognition Sequence for
H
indIII