CHAPTER 19: GENE TECHNOLOGY

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Dec 3, 2012 (4 years and 10 months ago)

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CHAPTER 17: BIOTECHNOLOGY


WHERE DOES IT ALL FIT IN?


Chapter 17 investigates contemporary uses of biotechnology based on the principles of classical and
molecular genetics. This chapter gives the instructors many opportunities to ask students critical
th
inking questions about applications of genetics knowledge. The topics in this chapter also stir much
debate in society and should be addressed as part of the coverage. Chapter 17 is the capstone chapter
for gene expression coverage from Chapters 15 and 16
of the book should be revisited when
covering genomics information in Chapter 18.


SYNOPSIS


Science has reached the exciting, but potentially dangerous stage, at which we are learning to
manipulate the materials of heredity. The first human genes isolate
d and inserted into bacteria
turned these cells into miniature factories producing interferon. Many bacteria possess restriction
endonucleases to protect themselves from invading viruses. Scientists use these enzymes to chop
up strands of DNA at specific l
ocations. Such specificity assures that a given enzyme will always
break up a specific kind of DNA into exactly the same size and number of fragments. These
fragments constitute a library of DNA sequence information. Restriction enzyme specificity also
ass
ures that all of the fragments possess identical, short sequences called “sticky ends.” Each
strand of a sticky end is complementary to the other strand and can be joined to the other ends
when treated with a DNA ligase. DNA Fragments, even those from diff
erent organisms, that
have been cut with the same restriction enzyme can be joined enabling the insertion of foreign
genes into a plant, animal, or bacterial genome.


Bacterial plasmids and viruses are the vehicles by which such genes are inserted into the

host
DNA, the crux of genetic engineering. There are four steps in this process: cleavage, producing
recombinant DNA, cloning, and screening. Cleavage is accomplished using the restriction
endonuclease that will produce the desired sticky ends. The fragme
nts are then inserted into the
desired vehicle. Unfortunately, very few vehicles actually receive DNA fragments and even
fewer get the desired piece. At this point, vehicles not carrying fragments are eliminated,
generally by prior association with an anti
biotic resistance gene. Each colony of cells is cloned
and allowed to multiply, thus replicating not only its own genome but the added fragment as
well. The clones are then screened to determine which clonal line contains the desired fragment.


Polymerase
chain reaction is another new molecular technique that amplifies DNA in an in vitro
sample. Frequently the DNA in a sample (of blood for example) is so small that it cannot be
analyzed directly. With PCR, the DNA is copied using a microprocessor
-
controlled

thermoregulator. The DNA unzips as the temperature is increased. When it is lowered,
polymerase enzymes catalyze the replication of DNA from special primers, making a new strand
from each original strand. Thus the amount of DNA is doubled at each cycle


2 strands to 4
strands to 8 strands to 16 strands and so forth. This method is substantially quicker than cloning
the DNA strand via plasmids or viruses. DNA is readily identified using a technique called
Southern blotting. Differences in DNA sequences are

identified by RFLP analysis. Each
individual can be identified by the RFLP patterns possessed, what is referred to as a DNA

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fingerprint.


Biotechnology uses genetic engineering techniques to solve practical problems. The biological
community is busy seq
uencing the entire human genome, certainly an enormous task. DNA
fingerprinting has been used to identify and convict numerous criminals. Dozens of commercial
applications exist to utilize this revolutionary technology. The most obvious application,
pharma
ceuticals, however, encounters additional problems of separating the desired product
from the rest of the cellular material. Attempts are being made to construct piggyback vaccines,
placing genes coding for the exterior of a virulent virus within the harml
ess vaccinia virus.
Agricultural uses range from developing resistance to herbicides, viruses, and insects; to
inserting genes for nitrogen fixation and improving growth and plant nutritional value.


Society must be informed about these biological process
es to ensure our safety and economic
well
being, as well as that of future generations. Lack of sufficient biological knowledge is the
source of most of the public’s concern about genetically engineered products. Many assume that
BST in milk products may c
ause human growth problems; they lack the physiological
knowledge that this protein is degraded in the stomach like all other
proteins. A great many people
do not trust governmental safeguards and fear the inadvertent or intentional development of lethal
v
iruses and bacteria. Although there is little scientific need for labeling genetically modified food
products, the public has the right to insist upon it. If properly done, labeling should serve to educate
consumers as well as inform them.



LEARNING OUTCO
MES




Understand the importance of plasmids and viruses to genetic engineering.



Know the natural function of restriction endonucleases and how a normal bacterial cell protects
its DNA from their activity.



Understand how “sticky ends” are formed and their im
portance to gene technology.



Describe how a chimeric genome is constructed.



Explain the four steps of genetic engineering experiments.



Distinguish between the techniques of selection and screening of clones.



Explain how to screen for clones that contain a
desired gene fragment.



Understand the value of and the processes involved with the polymerase chain reaction (PCR).



Describe techniques used to characterize DNA.



Discuss the different applications of gene technology.


COMMON STUDENT MISCONCEPTIONS


There
is ample evidence in the educational literature that student misconceptions of information
will inhibit the learning of concepts related to the misinformation. The following concepts
covered in Chapter 17 are commonly the subject of student misconceptions.

This information on
“bioliteracy” was collected from faculty and the science education literature.




Students believe that all biotechnology is genetic engineering



Students do not fully understand the role of genetics and environment on determining

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observa
ble variation in organisms



Students do not differentiate the genetic differences between prokaryotes and eukaryotes



Students believe that genetic modification is more unpredictable than selective breeding
in determining an organisms characteristics



Student
s believe that genetically modified organisms are inherently dangerous



Students believe that genetically all modified foods are unsafe or cause allergies



Students believe that gene transfer introduces many characteristics of one organism into
another



Stude
nts believe the virus vectors used in gene transfer are more dangerous than natural
viruses



Students believe it is not possible to introduce the genes of animals into plants



Students believe it is not possible to introduce the genes of plants into animals



Students believe that cloning is an unnatural process



Students believe that genetic modification and cloning introduces unpredictable
mutations


INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE


Here we have what’s happening in biology today; where the mone
y is to be made!


Discuss the mechanisms of gene technology before discussing its implications. Students have a
hard time with the nature of the “sticky ends” resulting from treatment with restriction enzymes.
To complicate matters, some blunt cutting enzy
mes have been discovered as well. It might be
helpful to present them with several DNA sequences and show how different restriction enzymes
would fragment the sequence. You can then show how identical “sticky ends” can be joined
together.


Genetic enginee
ring would be significantly more difficult without plasmid and viral vectors.
Plasmids were presented in the last chapter, viruses were discussed to some extent in the chapter
before that. Recall in either case, how the vector is naturally able to insert g
enetic material into a
complete genome, the plasmid into bacteria, the virus into eukaryotes causing some forms of
cancer. Science is merely adapting a natural phenomenon to its own benefit.


Screening is not only the most difficult part of genetic enginee
ring to do, it is the hardest part to
understand. Include the presence of the antibiotic resistance gene at the onset of your discussion.
Explain its function at the screening step. The many technical terms associated with gene
technology can be confusing;

most are associated with genetic engineering in that they are means
for identifying the cell with the correct stuff.


Probes have been developed for a number of tumor cell lines and Huntington’s disease. The
latter is 95% to 98% accurate in determining wh
ether the gene is present. Thus persons with the
disease in their family background can be tested long before the onset of the disease itself (most
individuals refuse testing or are tested and don’t want to be told the results). Knowledge of test
results m
ay impact personal lifestyle and plans for having children as well as insurance and
health policies.



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One merely needs to pick up the science section of the weekly newspaper, or a lay science
magazine to see examples of gene technology in action. As a resu
lt, it is important to discuss the
implications of such research and the necessary scientific and governmental regulations. This is
one of the stronger reasons to have some knowledge of biology, to be able to make informed
decisions, and to determine if th
e decisions made by those in power are indeed in the best interest
of the populace. Someone will need to make difficult decisions in the not
-
so
-
distant future. Just
because science can perform certain technological feats doesn’t mean that it should be allo
wed to
do so. Conversely, just because some gene technology is potentially dangerous, doesn’t mean
that all related technology should be brought to a halt. It’s your students who will be making the
political decisions for the future of the world.


HIGHER L
EVEL ASSESSMENT


Higher level assessment measures a student’s ability to use terms and concepts learned from the
lecture and the textbook. A complete understanding of biology content provides students with the
tools to synthesize new hypotheses and knowled
ge using the facts they have learned. The
following table provides examples of assessing a student’s ability to apply, analyze, synthesize,
and evaluate information from Chapter 17.


Application



Have students design a theoretical vector for introducing a b
acterial gene
into an animal cell.



Have students hypothesize about feasible traits that can be introduced into
crops.



Ask students to hypothesize how ligase can be used to make new genes..

Analysis



Have students to compare and contrast traditional selecti
ve breeding to
genetic engineering as a means of producing new agricultural organisms.



Ask students to determine the problems of introducing eukaryotic DNA
into prokaryotes using genetic technology.



Ask students to explain why it is possible to damage exi
sting genes when
new genes are introduced into genomic DNA
.


Synthesis



Ask students develop a hypothetical expression vector that would prevent
genetically modified crops from reproducing with related wild plants.



Ask students develop ways of using restr
iction enzymes as a tool for
controlling viral diseases.



Ask students come up with a way strategy of using plants to remove
hazardous wastes from the soil.

Evaluation



Ask students to
evaluate the pros and cons of growing genetically
modified crops such as

bt corn
.


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Ask students to assess the value of cloning in agriculture.



Ask student to debate the safety concerns associated with the creation of a
new gene.


VISUAL RESOURCES


Palindromes are words that exhibit two
-
fold rotational symmetry (bob, kook, deed
). The phrase
“a toyota” is a palindrome as is “a man, a plan, a canal, panama.” Search the web for thousands
of examples, but start here:
http://www.cs.rdg.ac.uk/archive/evihcra/

ku.ca.gdr.sc.www/
/:ptth/.
Hopefully you will notice that the URL itself is a palindrome!


The scifi film “Gattaca” touches on future (or maybe not so future!) gene technology and the
ethical implications of genetic control. Substantial infor
mation is available at the movie website

http://www.sciflicks.com/gattaca/.


IN
-
CLASS CONCEPTUAL DEMONSTRATIONS


A. Virtual Vector



Introduction



This demonstration provides a tangible model for showing s
tudents design elements of an
expression vector.


Materials




Thick permanent markers



White clothesline or thick rope



Yellow wool or twine



Red wool or twine



Blue wool or twine



Green wool or twine



1 inch thick slivers of duct tape



Scissors



Procedure & Inq
uiry


1.

Review the use of an expression without describing its components .

2.

Tell the students you will be using rope to represent a plasmid to be used as an expression
vector

a.

Take a 2” loop of white clothesline or rope and tape it into a loop

b.

Tell the class
that the loop can be a plasmid or a yeast artificial chromosome
(YAK).

3.

Then ask the class what they would need to make a eukaryotic expression vector.


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4.

Use the materials in the following manner as the class is making suggestions:

a.

Use the scissors to repres
ent restriction enzymes for cutting open the plasmid

b.

Use the duct tape to present ligase bonded regions of the vector

c.

Use the wool or twine to represent different components of the vector

5.

Cut an paste the expression vector based on students comments

6.

Then h
ave the class evaluate the accuracy of their vector


B. Virtual Biotechnology Concept Map



Introduction



This fun and fast way to build a concept map engages students in developing a scheme
for reviewing all the facts and concepts associated with DNA rep
lication. It helps student select
relevant information needed to understand DNA replication. In addition, it helps them
incorporate concepts learned in other sections of the book that contribute to an understanding of
DNA replication. The simple click and
drag animated concept mapping tool should be practiced
before using in class.


Materials




Computer with live access to Internet



LCD projector attached to computer



Web browser with bookmark to Michigan State University C
-
Tool:
http://ctools.msu.edu/ctools/index.html



Procedure & Inquiry


1.

Tell students that you would like to do a quick review of the concepts associated with
DNA replication.

2.

Then go to the Michigan State University C
-
Tool and add the co
ncept map term
“Biotechnology”. Use the “Add” and “Concept Word” feature to place a term on the map
background.

3.

Solicit a few more terms or concepts and then ask the class how the concepts are
connected to each other. Use the “Add” and “Linking Line” feat
ure to build a connecting
line.

4.

Then ask the students to justify the concept linking lines. Use the “Add” and “Linking
Word” feature to place student comments on the map.

5.

Continue the activity until you feel the students made a comprehensive map.


USEFUL
INTERNET RESOURCES


1.

Animations are a valuable classroom resource for reinforcing the DNA concepts needed
to understand biotechnology. The Cell Biology Animation website provides a well
-
done
animation sequence showing the three
-
dimensional structure of DNA

and its location in
the cell. This website can be
found at
http://www.johnkyrk.com/DNAanatomy.html

2.

Gene and vector bank databases are valuable tools used by researchers who desing

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expression vectors
. Students can be shown how these databases are used by looking up
different types of vector components available to researches.
A website maintained by
the Human Genome Project links to gene and vector resources that can be shown on an
LCD project. The w
ebsite can be found at
http://www.biologia.uniba.it/rmc/0
-
1a_pagina/1
-
1_PAC.html
.

3.

The history of biotechnology is an interesting topic discuss with students during a lecture
on biot
echnology. Excess Excellence has a biotechnology timeline that can be projected
on a screen to review with students.
The website is available at

http://www.dna.gov/
.

4.

Case studies are a highly effective way to reinforce
the learning of issues related to
biotechnology. A case study developed by the University of Buffalo called
“Frankenfoods? The Debate Over Genetically Modified Crops” encourages students to
rationally investigate the scientific and societal issues related
to genetically modified
crops. The website can be found at
http://www.sciencecases.org/gmfoods/gmfoods.asp
.


LABORATORY IDEAS



Biotechnology research requires computational studies using a
DNA database before
proceeding with the laboratory work needed to produce a genetically modified organism. This
activity introduces students to the use a DNA sequence search engine called BLAST.


a.

Introduce students to the value of knowing gene sequences b
efore designing expression
vectors used to produce genetically modified organisms. Tell them that researchers use
electronic on
-
line databases to search for gene sequences for a particular protein they
want to place into an organism.

b.

Provide students with
the following resources:

a.

Computer with Internet access

b.

Web browser with a bookmark to BLAST Tutorial
(
http://www.ncbi.nlm.nih.gov/Education/BLASTinfo/information3.html
)

c.

Web
browser with a bookmark to BLAST Search
(
http://www.ncbi.nlm.nih.gov/blast/index.shtml
)

d.

A list of amino acids with their single letter designations

e.

Codon chart

c.

Tell the students go the BLAST tu
torials on Information Page of the BLAST website.

d.

Then tell the student to type in the amino acid sequence into the Input box on Part 2 of
the PSI
-
BLAST tutorial at
http://www.ncbi.
nlm.nih.gov/Education/BLASTinfo/psi1.html
:

a.

GLNKSVEEFENELKNKLTEEAKNKMENIKKELEDVGFKVKDIIVVGIPHEE
IVKIAEDEG

b.

Have them press the Search button without making any other changes to the
search.

c.

Then have them discuss with each other the diversity of genes program
ming that
amino acid order in its DNA sequence.

e.

Now have the students go to the BLAST Search and click on the Protein
-
protein BLAST
(blastp) link.

f.

Instruct them to type in the same amino acid sequence and analyze the results.

g.

Then have them analyze the re
sults including any information provided in the links from

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the completed search page.

h.

Then instruct the students to calculate the approximate DNA sequence for the gene.

i.

Have the students go to the Nucleotide search and type in the purported DNA sequence.

j.

Have the students assess the outcomes of their search. They should be able to explain
why the search may or may not have found the appropriate gene for the amino acid.


LEARNING THROUGH SERVICE


Service learning is a strategy of teaching, learning and refl
ective assessment that merges the
academic curriculum with meaningful community service. As a teaching methodology, it falls
under the category of experiential education. It is a way students can carry out volunteer projects
in the community for public age
ncies, nonprofit agencies, civic groups, charitable organizations,
and governmental organizations. It encourages critical thinking and reinforces many of the
concepts learned in a course.


1.

Have students do a presentation on biotechnology to a civic group.

2.

Have students design an educational PowerPoint presentation of genetic engineering for
high school teachers.

3.

Have students tutor high school biology students studying genetics.

4.

Have students design a series of educational posters about biotechnology for
a local
school or library.