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sandwichtumtumBiotechnology

Dec 16, 2012 (4 years and 9 months ago)

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Biotechnology &
SynBio

By C. Kohn, Waterford WI

Better Bushels


Imagine if we had a crop that produced its
own pesticide…


We wouldn’t have to spray fields with a chemical
pesticide


This would save farmers money and protect the
environment


It would also reduce the pathogens that affect
our crops, reducing the need for other protective
treatments while making fields more productive.


Would this be a good thing or a bad thing?
Discuss

Bt

Corn


Such a product does exist and has been used
for over 15 years.



In fact, 45% of the corn grown in the US is
genetically modified.



The most famous

example of this is

Bt

Corn.


Left: Control


Right:
Bt

Corn

Bt Corn


Bt

Corn is a GMO, or Genetically Modified
Organism.


GMO
: a plant or animal that
has
been genetically
modified
through
the addition of a
small
amount
of genetic
material
from other organisms.



In a GMO, genetic material from another
organism is inserted into the plant or animal
genome.


These genes can come from any living source, including
bacteria, fungi, and other organisms.


Bt

=
Bacillus
thuringiensis


In the case of
Bt

Corn, an inserted gene for a
natural insecticide came from
Bacillus
thuringiensis
,
a bacterium found naturally in the soil.


B.
thuringiensis

bacteria naturally produce a toxin (the
Bt

delta toxin) which kills specific predatory insects
during the larval stage.


It does not
harm other
insects in the way broad
-
spectrum insecticides do,

making
it an
ideal replacement

to
synthetic
chemical
pesticides.


Bt

was actually available

as
a separate pesticide

since
1960 and has an

excellent
safety record,

making
it an ideal choice

as
a GMO.


Production of Bt Corn


Production of Bt Corn was relatively
straightforward:

1.
The gene for the Bt toxin was sequenced and

identified.

2.
The gene was removed from the
B.
thuringiensis

genome using a restriction
enzyme.

3.
The genome of corn was spliced using the
same restriction enzyme.

4.
The gene was inserted and made permanent
using DNA ligase.

5.
The modified corn genome was inserted into
a

corn cell nucleus.

6.
The corn cell, when it divided, produced the Bt

gene along with the rest of the corn’s genome.

Bt in action.


Because Bt corn has the gene for the Bt toxin,
it produces this protein just like any other
protein in a corn cell.



When an insect ingests the Bt toxin protein
produced by the corn, the Bt toxin binds to the

stomach wall of the

insect.



Within hours the stomach

wall is broken down by

the toxin.


Bt & Monarchs


Concern has been raised about the
impact of Bt corn on monarch
butterflies.



Research
by the USDA’s Agricultural
Research Service has shown that
other than an early version of Bt Corn
(which has since been replaced), the
impact on monarchs is negligible and
insignificant.


Plus, the alternative to Bt corn is the use
of chemical pesticides, which are far
more harmful to butterflies.

Is It Safe?


Bt corn was approved by the USDA for human consumption in 1995.
Is it safe?


This might be a good question, given the Bt toxin kills insects by destroying
their intestinal tracts




Delta
endotoxins

and VIPs produced by the currently available events all
are rapidly broken down in the stomach and thus are not potential food
allergens
.”


Colorado State University


i.e. your own stomach will rapidly break down the toxins before they can
affect you



Bt corn is considered generally safe a not a threat to consumers.


It is regulated by both the

EPA and FDA for human

and environmental safety.


It has been used for over 15

years with no record of

serious issue.

Biotechnology


Bt

Corn has become the poster child of biotechnologies made
possible by recombinant DNA
.



Recombinant DNA has made the science of biotechnology
possible.


Recombinant DNA
: when genes from two different species are
combined and introduced into a
cell


Biotechnology
: the manipulation of the genetics of organisms to
make useful products



Biotechnology is not necessarily a new science


Selective breeding of livestock and the use of microbes to make wine
are ancient examples of

biotechnology



However, with the use of

recombinant DNA and other

technologies, biotechnology

has changed modern life.

Making Recombinant DNA


Production of recombinant DNA is similar
regardless of what you are producing.



First, a gene must be cut using a restriction
enzyme (a chemical scissors for DNA that
always cuts at the same sequence of bases)


Copies of DNA always

yield the same restriction

fragments when exposed

to a restriction enzyme

(meaning DNA copies

are always cut in a

predictable way).

Making Recombinant DNA


If a restriction enzyme cuts DNA in such a way
that a single
-
stranded portion remains, this is
called a “
sticky end




Sticky ends are important because they allow the
addition of new genes so long as they have the

complementary sequence to the

sticky ends


E.g. a new gene would have

to have a TTAA sticky end

to ‘fit’ inside these restriction

fragments.



Creation of Recombinant DNA


1. A restriction enzyme cuts DNA


2. Restriction fragments are created


3. A new gene with complementary sticky
ends is inserted.


4. DNA
ligase

(an enzyme) permanently
seals the new gene into the genome.

Restriction

Enzyme

DNA

Ligase

DNA
Ligase


DNA ligase
enzyme is necessary to “cement”
the new gene into the genome.


Without DNA
ligase
, the bond is only temporary.


DNA
Ligase

is the “super glue” that makes a bond
permanent



Once DNA
ligase

has formed a permanent
bond with the new gene and the original
genome (the “vector), we have recombinant

DNA.


A
cloning vector
is the

DNA that carries the

inserted gene

Biofuels


Scientists are currently working to develop GM organisms
that can convert cellulose (in plant cell walls) into (such as
ethanol and biodiesel).



Scientists are working to identify the genes responsible for
more efficient breakdown of cellulose and how and where to
insert these genes into the genome of modified organisms
like
E. coli

and yeast.



The hope is that an organism

could be developed to either

breakdown cellulose more

efficiently than we currently

can with yeast produced

through selective breeding.


Synthetic Biology


The use of recombinant DNA in biotechnology has led to
the rise of a new science: synthetic biology.


Synthetic Biology: a science combining engineering,
biotechnology, and biology in order to create new biological
organisms that do not exist naturally in the environment.



In a sense, synthetic biology is the combination of genes from
different sources to create a “super organism” that can do all
the things we need it to do.



By selectively choosing and

inserting genes, the hope is

that we can create organisms

from scratch that can address

the most pressing needs facing

society.

Examples of
Syn
-
Bio Attempts


Synthetic Biology has been used so far to
address the following:


The production of more productive microbes for
the rumens of cattle


Production of more potent and effective vaccines


Production of bio
-
engineered drugs that target
and destroy cancer tumors


Bioremediation microbes that can quickly clean
up an oil spill or toxic waste


Biofuel
-
producing microbes that can convert
plant
feedstocks

into more useful substances
(cellulose into glucose for ethanol or oil for
biodiesel).

The Moral and Ethical
Implications


If a product of synthetic
biology were to
escape
into
earth’s fragile, complex and highly
interdependent
ecosystem, it could
have
devastating effects on all naturally occurring
organisms.


Our “super organisms” could become super
-
invasive,
seriously disrupting natural processes.


The unintentional release
of
synthetically
engineered organisms could have damaging
side
effects.


Many
who
oppose
this type of research fear that
this science could be abused may
fall into the
hands of terrorist groups and rogue nations.


Current Research


Watch the following
video



Recombinant DNA, as advanced as it is, is even
being phased out by advances in
SynBio
.



Use of recombinant DNA was sort of like writing
a book using words and sentences from other
books.


Scientists now are trying to create genes from scratch
that could be inserted into cells, enabling them to
write their “book” from scratch rather than trying to
find the genes responsible for the traits they are
trying to create. .

SynBio

& Malaria


One of the first major successes with Synthetic
Biology was the production of precursor to
the
compound
artemisinin
.


This compound has
been shown to be effective
against strains of
malaria that
are resistant to
more
widely
-
used drugs


However, this drug was far too expensive to produce



"By inserting genes from three separate organisms
into the E. coli, we're creating a bacterial strain that
can produce the
artemisinin

precursor
.
" Jay
Keasling
,
lead researcher on the project.

SynBio

Malaria Medicine


Keasling

and
his team took genes
from
yeast and from the sweet wormwood
tree
(the source of the drug compound)
and inserted them into
E
.
coli
.



As a result,
the yield of the
artemisinin

precursor
in
that
strain
of

E
. coli

was increased by

10,000 times compared to

that of the wormwood tree.


Right:
Keasling

and the

wormwood tree


Photo courtesy of:
www.lbl.gov


Biofuel of the Future


If we were to create a similar organism as
the malaria
-
drug
E. coli

bacterium, what traits
would it need?



Think/Pair/Share


what kinds of genes
would we need to insert into yeast or
E. coli

in order to produce the ideal biofuel
microbe?


What aspects of this work might interfere
with the function of this modified organism?


E.g. does it matter where the gene is placed?

Problems With
SynBio


If we continue our book analogy, writing a book is far harder
than copying and pasting text from other publications (which
is why plagiarism is so bad among students;)



For example: does the placement of the word in a sentence
matter?


In sentence: does the matter of the example in a of matter
placement?


Obviously, it does.



The same is very true for genes


we can’t just lob it in the
genome somewhere


the placement of a gene will very
much affect how effectively the gene is expressed.

More Problems


Another problem with
SynBio
, as well as any modified
genetics, is that modified organisms can lose their
competitiveness as they become more and more
modified.



Many modified organisms lack the ability to compete
to the extent that they cannot function outside of a
lab setting.


Obviously this would be a problem for the industry.



There is no standard way to modify an organism
and

make it competitive and functional outside of a lab.


This makes trial and error a big part of this process.