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Case Study: Gene, gene cloning and biotechnology
Key Concept:
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Overview of Gene and Nucleic Acids
Structure of DNA, DNA Sequences and Restriction Enzyme
Introduction of Gene Cloning, Genetic Engineering and Biotechnology
Ethnical, social and economical issues in Biotechnology and Gene Therapy
Materials Preparation:
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Prior to the class, search information, such as news articles relating to gene, gene
cloning and biotechnology.
Suggested activities:
1.
Have a class discussion about genes. Explain that genes are inherited from parents
and are important because they determine much about behavioral, mental, and
physical traits. Every gene contains a DNA (deoxyribonucleic acid) code that gives
the cell instructions about how to make specific proteins. These proteins form the
basis for the structural framework of life.
2.
Encourage students to discuss on the following:
1.
Issues on the new genetic research – students may write their ideas on a large
sheet of newsprint, discuss cloning animals, using DNA in criminal
investigations, or gene therapy for some types of genetic diseases and cancer.
2.
Issues on biotechnology, gene cloning and genetic engineering. For example,
the technology may allow a 60-year-old woman to have a baby. Is that a
positive or negative outcome? Consider its ramifications.
3.
It took scientists 277 attempts to clone a normal, healthy sheep (Dolly). But what
happened to the other 276 sheep? Encourage students to research these previous
attempts and ask them to think about the consequences of cloning.
4.
Have students brainstorm the risks and benefits associated with biotechnology. For
example, the removal of hemophilia or other serious disorders from the gene pool is
a benefit because people would no longer suffer from a chronic condition. An
example of a risk is going too far in selecting the genetic makeup of future children.
Possible risks:
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Selection of the genetic makeup of future children. This practice may give
people the power to control some personal traits, such as having blond hair or
being tall. Taken to an extreme, this could eliminate some traits.
Using biotechnology before exploring other options, particularly in
reproductive medicine. For example, technology enables scientists to implant
an egg from one woman into the uterus of another. But it may not be a good
idea to use this technique before trying less extreme techniques first.
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Possible benefits:
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Eliminating genetic diseases. For example, geneticists think it may be possible
to eliminate genetic diseases such as Tay-Sachs through careful and
methodical screening programs.
Screening unborn babies. This refers to screening for genetic disorders either
before a pregnancy takes place or in the early months of a pregnancy. More
information would give prospective parents more options in dealing with their
infants’ problems.
Treating diseases. For example, scientists are working on ways to insert cells
from embryos into cancerous cells as a way to stop the growth of cancer.
Reference:
1. http://www.accessexcellence.org/AE/AEPC/BE02/gentest/fail15.html? Cloning
Genetic Science Learning Center “Teacher resources” –
(http://gslc.genetics.utah.edu/teachers/)
2. Biotechnology – (www.zoo.ufl.edu/PCB3063/biotech handout.pdf)
3. Molecular Genetics –
(http://fig.cox.miami.edu/~cmallery/150/gene/mol_gen.old.htm)
4. Cloning Fact Sheet –
(http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml#whatis)
5. What is Biotechnology – (www.aitc.ca/bc/media/BioTechS1.pdf)
6. Biotech Kids Carnival – (http://www.swmed.edu/stars/resources/stock02/Riddle.doc)
7. AACAES : Educators : Science Activities –
(http://www.uga.edu/discover/educators/environmental_science/activities/qcc34.ht
ml) / (http://www.uga.edu/discover/educators/applied_bio_chem_2/all/all10.html)
8. Isolation DNA – (http://fog.n4h.org/f33.htm)
9. A Feast For Our Future –
(http://www.accessexcellence.org/AE/AEPC/WWC/1992/transgenic_food.html)
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Prepare notes and questions to be discussed before the session:
Level of difficulties:
[1] Prior concepts
[2] Essential concepts
[3] Big and global concepts
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1.
Discovery of inheritance [1]
The mechanism of inheritance was discovered by Gregor Mendel
(1822-1884), an Austrian monk who crossed different pea plants
and noted the manner in which different characteristics of coloring,
of seed appearance, of length of stem were developed. This led to
the proposal of “the Mendelian laws of inheritance.” However, he
did not know the factors responsible for inheritance.
For details, visit:
Gregor Mendel –
(http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.html)
(Photo adapted from:
http://tidepool.st.usm.edu/crswr/103inheritance.html
http://www.uwinnipeg.ca/~simmons/cm1503/mendel.htm)
2.
In the early twentieth century, it became clear
the factors were something called “genes”
which were found in chromosomes in the
nucleus of a cell. [Now, it is known that genes
are made up of deoxyribonucleic acid (DNA)
packaged in compact units in chromosomes.
One strand of DNA, approximately 3 meters
long, contains many genes. All these genes
give instructions for how to make and operate
(Photo adapted from:
the parts in our body.]
http://www.toyamampu.ac.jp/ph/yakka/research/p3.html)
Gene and nucleic acids
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In 1869, Friedrich Miescher, a German chemist, found a “new” class of acid substance from
pus cells (also salmon sperm heads) that was not carbohydrate, lipid, or protein. (At that
time, organic substances were classified into these three broad groups.) Since the substance
was isolated from nuclei, it was later named nucleic acid.
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In around 1910, it was found that nucleic acid contained two purines adenine (A) and
guanine (G), and two pyrimidines, thymine (T) and cytosine (C), all in equimolar amounts.
These are called bases.
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
In the mid twentieth century, both circumstantial and direct evidence suggested the role of
deoxyribonucleic acid (DNA) in heredity. It is now known that DNA is the genetic material
except in the case of certain viruses which do not contain DNA. In such viruses the genetic
information is contained in ribonucleic acid (RNA).

All nucleic acids contain three components: a base and a sugar with a phosphate attached to
it. RNA differs from DNA in two major aspects: (a) RNA contains uracil instead of
thymine, and (b) the sugar is a ribose instead of a deoxyribose.

Now it is clear that a gene is a DNA sequence. A gene is a linear sequence of DNA that
contains all information necessary for the production of a protein and different types of
RNA.
In human, there are 46 chromosomes (22 pairs of autosomal chromosomes and 2 sex
chromosomes, X and Y). They house almost 3 billion base pairs of DNA that contains
about 30,000 - 40,000 protein-coding genes. The coding regions make up less than 5% of
the genome (the function of the remaining DNA is not clear) and some chromosomes have
a higher density of genes than others.
3.
Structure of DNA [1]
In 1953, Wilkins, MHF and associates
based on their x-ray diffraction (a
technique that enable molecular
biologists to construct the 3-dimensional
structure of a molecule) study proposed
that a DNA molecule contained helical
chains, like a twisted ladder. In the same
year, Watson JD and Crick FHC, based
on
their
and
other
scientists’
biochemical findings, proposed the
double-helix model of DNA in which A
paired specifically with T, and G with C.
The means that the two strands are
complimentary and that the nucleotide
sequence on one strand determines that
on the other.
O
OH
P
-
O
O
HO
H2C
O
O
A
T
O
CH2
O
O
O
H2C
CH2
O
O
H2C
O
O
O
CH2
O
O
P
O
O
A
O
T
O
HO
-
O
O
H2C
O
G
C
P
-
O
P
O
O
-
O
P
O
O
C
G
O
O
-
O
P
O
O
-
O
P
-
CH2
-
O
O
P
OH
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Some basic features of DNA and RNA
DNA
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a double stranded helix
“rungs’ in the ladder of the helix joined together by hydrogen bonds
phospodiester linkages between 5’ & 3’ ends of nucleotides; 5’ 3’ direction
contains deoxyribose sugar
contains A, T, C, G nucleotides
found in the nucleus of cells; some is found in the mitochondria
RNA
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primarily a single stranded molecule
linked by the same type of phosphodiester bonds that join DNA together; 5’ 3’
direction
contains ribose sugar
contains A, U, C, G nucleotides
3 types of RNA – messenger, ribosomal & transfer (mRNA, rRNA, tRNA)
found in the cytoplasm; however it is manufactured in the nucleus, so some is found
there
Most naturally occurring DNA molecules are so long that to determine the sequence of the
whole molecule in one operation would be unthinkable. For example, there are about 4 x
106 base pairs in the entire genetic content of Escherichia coli (E. coli), an intestinal
bacterium.
(For detail about DNA, genes and chromosomes visit: Tour of the Basic
(http://gslc.genetics.utah.edu/units/basics/tour/)
4.
DNA sequencing [2,3]
In order to decode the secret information stored in a DNA molecule, it is necessary to find
out the sequence of bases in it. Because DNA is such a long molecule, how do we know
where is the head? Where is the tail? Fortunately, there are restriction endonucleases which
cleave DNA at specific base sequence they recognize, hence named restriction enzymes. An
endonuclease is a pair of DNA scissors that catalyzes (hydrolytic) cleavage of a DNA
molecule at specific base sequence.
For example, HaeIII, a restrict enzyme, cleaves in the middle of the
sequence …..GG↓CC….. and no where else. BamHI makes a cut at G↓GATCC and PstI at
CTGCA↓G. Whenever this sequence occurs, this enzyme will make a cut. At present,
hundreds of restriction enzymes have been isolated and many of them are commercially
available. By using different enzymes (or enzyme combinations), we can obtain pieces of
shorter DNA fragments. By arranging these fragments, we can deduce the base sequence in
a DNA molecule.
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5.
Why do bacteria produce restriction enzymes? [2,3]
Restriction enzymes are found in a wide variety of microorganisms and play vital defense
role in bacterial cells. We know that viruses can infect a bacterial cell, if the cell contains a
set of restriction enzymes that cut up foreign viral DNA into pieces and destroy it as soon as
it enter the cell. The entry of such DNA would be “restricted.” Bacterial cells contain
special chemically modified DNA to prevent the attack on the host DNA.
6.
What is polymerase chain reaction (PCR)? [1,2]
DNA polymerase is an enzyme that is able to replicate a DNA molecule in the cell nucleus.
Replication of DNA requires DNA polymerase, a primer and nucleotides. PCR is a
technique that is designed based on the DNA replication in cells to amplify the number of
copies of a specific DNA sequence (or a gene) through cycles of denaturation (breaking the
helix into separate chains) and replication in a test tube.
Kary Banks Mullis was the inventor of PCR. For his invention of the PCR method, he won
The Nobel Prize in Chemistry 1993. PCR is a key technique in molecular biology and
biomedical fields that permits the analysis of any pieces of a short sequence of DNA
without having to clone it. Before the invention of PCR, amplifying of genes or DNA was
done in bacteria, and took weeks. But now with PCR, it takes only a few hours.
Three steps are involved in a PCR. These 3 steps are repeated for 35 or 45cycles. The cycles
are done in a machine called PCR machine or a thermo-cycler, which rapidly heats and
cools the test tubes containing the reaction mixture.
The 3 steps for one cycle take place at different temperatures and they are:
1.
Denaturation:
At 94°C, heat breaks the hydrogen bonds and the double-stranded DNA melts and
opens into single-stranded DNA.
2.
Annealing:
At 54°C, hydrogen bonds form between the "primer" and the single-stranded DNA
from samples. Primer is a short single-stranded DNA with known sequence designed
by scientists to amplify a particular gene. The single-stranded DNA from samples is a
template that provides the pattern to be copied. Since the number of primers is more
than that of the long complimentary strand of the DNA, primers form hydrogen bonds
with the single-stranded DNA from samples more easily than the long complimentary
strand .We call this step as annealing.
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3.
Extension:
After the annealing, the enzyme polymerase attaches to this double-stranded structure
and starts copying the template. At 72°C, the polymerase works best.
PCR is widely used in the biochemistry and molecular biology research, DNA
fingerprinting and DNA sequencing.
For animation of PCR in the Internet, visit:
i. RT-PCR Methodology –
(http://www.bio.davidson.edu/courses/Immunology/Flash/RT_PCR.html)
ii. PCR animated – (http://users.ugent.be/~avierstr/principles/pcrani.html
iii. Internet Resources –
(http://www.woodrow.org/teachers/esi/2002/Biology/Projects/p3/pcrinternet.htm)
7.
What is gene cloning? [1]
A clone is a population of organisms that are genetically the same as they are derived from a
single ancestor. For example, all of the bacteria in a colony on a culture plate are clones
because they were derived from a single bacterium. To clone a gene generally means to use
organisms to generate, through genetic engineering techniques, many copies of the specific
gene in question or interest.
Reference:
i.
Gene Cloning – (http://www.lsic.ucla.edu/ls3/tutorials/gene_cloning.html)
ii. Gene Cloning (animation) – (http://croptechnology.unl.edu/download.cgi)
iii. Human Cloning –
(http://www.bbc.co.uk/science/genes/gene_safari/clone_zone/human_cloning.shtml)
8.
How is a gene cloned? [2]
First, with the help a restrict enzyme, one can isolate a DNA sequence containing a gene.
Next, is to insert the gene into a vector (a carrier that would carry the gene into a host cell).
The most commonly used vectors are plasmids or bacteriophages because they can replicate
independently in a host cell, usually a bacterium like E.coli..
Gene Cloning Animation –
(http://www.mybiology.com/archive_movies/dna_tech_movies.htm)
9.
Since one can make copies of a DNA fragment by PCR, why do we still need to clone a
gene? [2,3]
PCR can only make copies of a small DNA fragment, but a gene is a very large fragment.
So, it would be very difficult (or inefficient) when compared to what a cell can accomplish.
Imagine if one wishes to obtain a large quantity of a particular protein (enzyme), one can
simply insert the gene into bacteria to generate many copies of the gene. Also, they would
do protein synthesis and we can collect the protein of interest later.
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PCR Animation:
http://www.lsic.ucla.edu/ls3/tutorials/gene_cloning.html
http://www.people.virginia.edu/~rjh9u/pcranim.html
http://www.abpischools.org.uk/resources/poster-series/pcr/pcranim.asp
http://www.rvc.ac.uk/Extranet/DNA_1/7_PCR.htm
http://www.mybiology.com/archive_movies/dna_tech_movies.htm
10. What is genetic engineering? [1]
By definition, genetic engineering is a scientific alteration of the structure of genetic
material in a living organism. It involves the production and use of recombinant DNA and
has been employed to create bacteria that synthesize insulin and other human proteins.
Therefore, genetic engineering is a process that alters the genetic makeup of an organism.
This technique provides remarkable opportunities to make a large quantity of protein,
insulin for example, and to develop new medical procedures to treat diseases. In addition to
revolutionizing some medical treatments, genetic engineering has much impact on food
production, fuel industries, mining and pollution control. It has been said, the effects of
genetic engineering to biotechnology is similar to microchips to information technology.
Reference:
i.
Say no to genetic engineering –
(http://www.greenpeace.org/international/campaigns/genetic-engineering)
ii. Genetic engineering and its danger –
(http://online.sfsu.edu/~rone/GEessays/gedanger.htm)
iii. Genetic Engineering – look ma! no math! –
(http://www.eurekascience.com/ICanDoThat/gen_eng.htm)
iv. Human Cloning and Genetic Engineering – (http://www.biofact.com/cloning/)
11. What is biotechnology? [1]
Biotechnology is the application of biological principles, organisms and products to
perform specific industrial or manufacturing processes. Some economists define it as the
use of biological organisms for commercial ends. Biotechnology is not a new technology;
brewing of beer, fermentation of wine, and production of cheese is almost as old as human
civilization. In brewing, carbohydrates from a variety of agricultural products (rice, wheat,
potato, etc) are subjected to fermentation usually by yeast to produce alcohol. Soy sauce has
been produced by microbial fermentation of soybean for hundred of years.
Since the early 1970’s, biotechnology has received a significant boost from the introduction
of a number of powerful new techniques known collectively as genetic engineering. These
techniques allow biological scientists to alter the genetic structure of organisms by adding
new genes/removing some existing genes that allow the organism to perform new functions.
Genetic engineering together with other ways of manipulating and using biological
organisms has provided new opportunities with profound implications for a wide range of
commercial activities, from agriculture to pharmaceuticals, chemicals, food and industrial
to processing, and mining.
Reference:
 Biotech Timeline - (http://www.ncbiotech.org/biotech101/timeline.cfm)
 Biotech – (http://bioweb.wku.edu/courses/BIOL115/Wyatt/Biotech/Biotech2.htm)
 Food Biotechnology - http://ific.org/food/biotechnology/index.cfm
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12. Applications of biotechnology in medicine [3]
One type of diabetes (insulin-dependent diabetes) is due to lack of insulin. Insulin acts on
certain cells (e.g. muscle cells) in our body to increase the entry of glucose into them and
this lowers the level of glucose in the blood. Insulin-dependent diabetes is treated by regular
injections of controlled amounts of insulin that serve to bring the insulin levels in the blood
to normal. This treatment requires a large quantity of insulin. The demand for insulin is
increasing rapidly because of the steady increase in diabetic patients. Until recently, the
supply was obtained from the pancreas (an organ that produces insulin) of cows or pigs.
This involves tedious isolation procedures. Moreover, if the insulin is contaminated, this
could be life threatening. Pharmaceutical companies saw the potential of this large and
lucrative market and attempted to produce insulin less costly and more efficiently.
Some medical products of genetic engineering
Product
Application and production source
Human insulin
Therapy for diabetics; produced by E. coli*
Interferon (alpha)
Possible treatment for cancer and viral diseases; produced
by E. coli
Hepatitis B vaccine
Prevent hepatitis B; produced by certain yeast that carries a
fragment of hepatitis virus gene
Taxol
Plant product used for treatment for ovarian cancer;
produced by E. coli
Human growth factor
Correct growth defects in children; produced by E. coli
Relaxin
Ease childbirth; produced by E. coli
(*E. coli is used to make most of these products because it is much less harmful and can
readily culture in a laboratory.)
Biotechnology can also be applied to cure diseases, and the procedure is known as gene
therapy. Gene therapy is a biotechnological technique for correcting defective genes with
healthy genes.
For more information about gene therapy, visit:
http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml#whatis
13. Application of biotechnology in agriculture [3]
Development of higher-yield crops, particularly rice and wheat, to satisfy the nutrition
needs of people of the less developed countries and to feed an ever-growing world
population had been put into action for many decades. The first wave of high-yield crops
came about through traditional cross breeding method – using knowledge gained from
Mendelian genetics to identify and select strains of crops that exhibit desirable
characteristics. However, there are still some disadvantages in the use of high-yield crops.
They generally required more fertilizer, more pesticide and herbicide treatments and better
irrigation. In short, more costly. Today, biotechnology has been applied to identify, select
and create strains that are more resistant to insects and drought and even strains that can
produce more nutrients (vitamins).
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Some medical products of genetic engineering
Product
Application and production source
Ice-minus bacteria
Lacks normal protein product that initiates undesirable ice
formation on plants; produced by P. syringae
Insect toxin producing Has toxin-producing gene inserted from B. thuringiensis;
bacteria
toxin kills root-eating insects that ingest bacteria
B. thuringiensis cotton Plans have toxin-producing gene from B. thuringiensis;
and corn
toxin kills insects that eat plants
Pork and beef growth Improve weight gain in pigs and cattle; produced by E. coli
hormones
Cellulase
Enzymes that degrade cellulose (a complex carbohydrate
that is very difficult to digest) to make animal feedstocks:
produced by E. coli
14. Application of biotechnology in fuel production [3]
The availability of energy reserves is getting lower and lower these days. Oil and coal are
more and more expensive. Countries without energy reserves have to spend a lot of their
national incomes to purchase energy. Some countries are actively exploring ways to find
alternative fuels to satisfy the demands, and some turn to biotechnology. One of the success
stories is the National Programme in Brazil launched in 1974. In Brazil, the most abundant
material was and still is sugar cane. Much of the sugar cane plant is disposed as waste after
sugar extraction. These leftovers are fermented to produce alcohol. In 1996, 14.5 billion
liters, or about 46 percent of the global total ethanol was produced using this procedure.
Some of alcohol produced is used to fuel cars and commercial vehicles.
15. Estimated worldwide biotechnological markets in 2000 [3]
Market sector
US$ (In millions)
Energy
15,392
Foods
11,912
Chemicals
9,936
Health care (pharmaceuticals) 8,544
Agriculture
8,048
Metal recovery
4,304
Pollution control
96
Source: (http://www.accessexcellence.org/RC/AB/IE/Biotech_Industry_Review.html)
Some ethnical, social and economical issues in biotechnology
As science continues to push the spectrum of biotechnological possibilities further,
economic profit for participating sectors and vast improvements in the quality of life for all
certainly await. However, before the benefits of applying such technology can be realized,
many scholars insist that the ethical, social and environmental consequences of altering the
natural genetic code must be thoroughly understood. Some of issues are briefly considered
below:
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16. Positive and negative issues in food biotechnology [2,3]
(a)
Positive issues
With a genetically improved seed, farmers have the ability to reduce expenses, obtain
higher crop yields, use less pesticide, produce a more nutritious, better tasting crop,
and provide a longer shelf life and better shipping properties.
For example, in an era when millions of people starve in third-world countries
because they cannot produce enough food to sustain life, biotechnology offers a hope
for the future. It has been hypothesized that in the future, modified seeds will allow
third-world farmers to continually grow food in areas with poor soil or irrigation by
developing crops that more efficiently absorb nutrients, also reducing the need for
costly fertilizers. Biotechnology could also help prevent disease and malnutrition in
the third-world by producing more healthful crops.
As a specific example, a strain of "golden rice" that contains high levels of iron and
beta carotene could be available within a few years, holding uncountable benefit for
the more than 100 million children who suffer from Vitamin A deficiency.
Furthermore, research is already in progress on developing fruits and vegetables that
could distribute life-saving vaccines simply through easily distributed, locally grown
crops. These are some positive aspects of food biotechnology.
(b)
Negative issues
On the other hand, the general public concerns about human allergic reactions to
altered food, the environment and the use of animal genes in plants. Take allergic
reaction as an example, the risk of potential allergens (substances causing allergic
reactions) in a genetically modified food is of particular concern because of the
possibility of transferring a gene that causes allergic reactions to a new food source,
without the consumer's knowledge of the transfer. If a gene from a food that
commonly causes allergic reactions, like in shellfish or peanuts, is inserted into a food
where people would not expect to find such allergens, then the food could potentially
harm the consumer. Although regulatory authorities closely monitor its safety, will
food on the market with said characteristics be labeled; with the information fully
disclosed to consumers?
Another common critique of food biotechnology concerns the environmental risks
involved in producing genetically altered foods. Would growing of the genetically
modified plant harm the surrounding soil, water, animals or other plants? Also, plants
and animals with clones genes may grow faster and they may upset the balanced
ecosystem and reduce the biodiversity.
Lastly, many consumers are concerned about their health when eating new sources of
food. Not to mention that some vegetarians “hate” eating genetically modified plants
with an animal gene.
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17. What is gene therapy? [2,3]
First discovered in the middle of the 1970’s researchers were able to isolate certain genes
from DNA. During the 1980’s the term gene therapy came about and propelled research
further.
Gene therapy is a technique where the genes causing a defect are themselves substituted by
“correct” genes in the patient to cure a disease. At birth, each of us receives a set of
chromosomes that contain the genes that code for our personality, appearance, and long
term-health. When one of those genes has a mutation or flaw in the DNA structure it can
lead to disease. Some diseases related to genetic inheritance are diabetes, sickle cell anemia,
and some cancers. With gene therapy we can eliminate these diseases before they even
show their first symptom.
18. Positive and negative aspects in gene therapy [2,3]
(a)
Positive aspects
The positive aspect of gene therapy is that it can wipe out genetic disease before they
can begin and eliminate suffering for future generations. Gene therapy is also a good
technique for diseases not researched yet. All of us carry defected genes and may not
know it. Gene therapy is a “medicine” for the future since it can control or eliminate
hereditary diseases.
In reality, every human carries nearly six defective genes. However, most of us do not
suffer any harmful effects from our defective genes because we carry two copies of
nearly all genes, one given to us by our mother and the other from our father.
Fortunately in most cases, one normal gene is sufficient to avoid all the symptoms of
disease. Nonetheless, about one in ten people has, or will develop at some later stage,
an inherited genetic disorder, and approximately 2,800 specific conditions are known
to be caused by defects (mutations) in just one of the patient’s genes. Some single
gene disorders are quite common, for example, cystic fibrosis is found in one out of
every 2,500 babies born in the Western World.
At present, the method of choice for delivering genes into cells uses the natural ability
of viruses to deliver genetic material to cells. (Viruses have evolved a way of
encapsulating and delivering their genes to human cells in a pathogenic manner.)
Scientists have tried to take advantage of this capability and manipulate the virus
genome to remove disease-causing genes and insert therapeutic genes. Currently, gene
therapy has only been approved to treat a limited number of diseases, including
adenosine deaminase in the US. Nonetheless, despite the low level of approved
treatments available today, many attempts are concentrating on applying gene therapy
to treat Parkinson’s disease, Huntington’s disease, thalassaemia, sickle cell anemia,
leukemia, autism and liver cancer. The future for gene therapy appears bright, as cures
for many of the most human diseases stand ready to be discovered.
(http://www.duke.edu/web/mms190/biotech/environmental.html)
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Reference:
 Living with a genetic disorder –
(http://www.nature.ca/genome/03/d/10/03d_14_e.cfm)
 Human Gene Therapy –
(http://www.ndsu.nodak.edu/instruct/mcclean/plsc431/students/zhou.html
 BIO. "Biotechnology in Perspective." Washington, D.C.: Biotechnology Industry
Organization, 1990.
(b)
Negative aspects
Despite promising evidence about the benefits of gene therapy, many hurdles must be
overcome before applying gene therapy effectively to treat diseases. Some of them are
due to procedural and/or methodological difficulties.
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Short-lived nature of gene therapy
Before gene therapy can become a permanent cure for genetic diseases, the inserted
DNA in target cells must remain functional and the cells containing the inserted DNA
must be long-lived and stable. However, the rapidly dividing nature of many cells
prevents gene therapy from achieving any long-term benefits.
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Immune response
Anytime a foreign object is introduced into human tissues, it may stimulate the
immune system to generate antibodies to remove them, and this reduces gene therapy
effectiveness.
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Problems with viral vectors
Viruses are employed as the carriers in most gene therapy studies, and some potential
problems associates with this method are: toxicity, immune and inflammatory
responses, and gene control and targeting issues. In addition, there is always the fear
that the viral vector, once inside the patient, may recover its ability to cause disease.

How can one control the expression? The number of genes incorporated? The amount
of protein synthesized?
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Multigene disorders
A number of diseases, such as heart disease, high blood pressure, Alzheimer’s disease,
arthritis, cancer, mental illness and diabetes, are caused by the combined effects of
variations in many genes. In all these cases, no one gene has the sole yes/no power to
say whether a person has a disease or not. It is likely that more than one genetic defect
is required before the disease is manifest, and a number of genes may each make a
subtle contribution to a person's susceptibility to a disease; genes may also affect how
a person reacts to environmental factors. Unraveling these complexed and
complicated networks of events will undoubtedly be a challenge for some time to
come.
13
Trial Version
In conclusion, due to a lack of conclusive evidence proving that genetic treatment has
produced therapeutic benefits, the future of gene therapy is still highly skeptical at present.
While the scientists made much progress in DNA technologies in food, medicine and
energy, perhaps the most important obstacle for further advancement in genetic technology
is to overcome its social and ethical implications. Each requires personal thought and
reflection to determine one’s opinion.
Some ethical and social issues are:
1.
Do we understand the risks and limitations of genetic technology? Would you trust the
assessment (or testing) of your doctor or a reputable scientist?
2.
Where is the line between medical treatment and enhancement?
3.
If you had your DNA sequence analyzed by a scientist, who owns and controls your
genetic information? Would you agree if he/she supplied it to an insurance company,
your (future) employer, or the police?
4.
Should genetic testing be performed when no therapeutic treatment is available?
5.
Are GM foods and other products safe to humans and the environment?
6.
How will these technologies affect developing nations' dependence on the developed
countries?
7.
In 1997, the European Commission found it difficult to ignore scientific evidence that
crops produced through biotechnology are indeed safe. The European Farm
Commissioner Franz Fischler approved an application to market gene-modified corn
produced in the United States in Europe, but it must fulfill some labeling conditions.
Do you think this requirement is reasonable and adequate?
For more information, visit http://www.fb.org/views/focus/fo97/fo0106.html.
Reference
1. Biotechnology Online - (http://www.biotechnologyonline.gov.au/)
2. Ethical, Legal, and Social issues –
(http://www.ornl.gov/sci/techresources/Human_Genome/elsi/elsi.shtml)
3. Gene watch – (http://www.genewatch.org/)
4. Introduction to nucleic acids and application to infectious disease detection (http://www.accessexcellence.org/RC/AB/BA/dnaintro/index.html)
5. Debate over GM products and biotechnology (http://www.ornl.gov/sci/techresources/Human_Genome/publicat/hgn/v12n1/06gmpr
oducts.shtml)
6. Gene therapy for cancer: questions and answers (http://cis.nci.nih.gov/fact/7_18.htm)
7. Gene therapy in simple terms –
(http://kidshealth.org/parent/system/medical/gene_therapy.html)
8. Scientific issues and social concerns –
(http://www.dnapolicy.org/genetics/transfer.jhtml;$sessionid$4I4DCIQAACY4WCQ
BAT3RVQQ)
9. Explain “What is a gene?” “Gene therapy” in simple terms –
(http://kidshealth.org/kid/talk/qa/what_is_gene.html)
10. Basics on genes and genetic disorders –
(http://kidshealth.org/teen/your_body/health_basics/genes_genetic_disorders.html)
11. Molecular Genetics –
(http://www.kensbiorefs.com/MolecularGen.html#anchor194140)
12. Using Genomics – (http://www.nature.ca/genome/index_e.cfm)
See also the block on “Stem cells and their applications”
Animation:
1. Tour of the Basics – (http://gslc.genetics.utah.edu/units/basics/tour/)’
2. DNA Workshop – (http://www.pbs.org/wgbh/aso/tryit/dna/#)
14
Trial Version
Local news [3]
Keywords
Title
基因影響阿士匹靈藥效
克隆野貓誕 8 小貓 瀕絕種生物有救
遲早樣樣吃不得
海洋細菌基因最少僅千三個
複製風險
水稻基因組序列全圖製成 有助解決饑荒
Newspaper
蘋果日報
文匯報
AM730
東方日報
新報
都市日報
Page number
健康與醫療 A20
國際新聞 A13
港聞 M06
國際 A29
觀點角度 F06
English news
digest 46
綠色和平戰船或來港示威
東方日報
港聞 A31
首隻複製狗意義重大
太陽報
社會及專欄 A33
把病毒戴上身
香港經濟日報 專題 C05
基因米疑流入港超市
蘋果日報
港聞 A18
科技展望 50 年： 記憶可下載 水果當藥食
明報
國際新聞 A23
復旦研究基因功能獲重大突破
大公報
中國新聞 A17
轉基因雜草抗除草劑
文匯報
國際新聞 A26
複製豬技術造紅血球生成素
東方日報
國際 A36
無改基因 煮熟不甩色
蘋果日報
國際頭條 A28
有助開發抗衰老產品 港大破解兒童早老症成因
大公報
港聞 A09
世衛：基因食物對人損害不大
東方日報
國際 A10
基因改造番茄抗沙士
蘋果日報
健康與醫療 A19
「有機耕作」農地須生態循環平衡
明報
輕 zone 特區 A20
複製豬心臟 有望移植人體 擁有人類基因年內擬先用 文匯報
國際新聞 A12
猴子作試驗
大豆油幾全屬基因改造
明報
中國社會 B16
吃基因玉米 老鼠腎異變 血液亦異常 專家憂對人類有 文匯報
國際新聞 A12
害
美 75%加工食品含改造成分
明報
國際要聞 A24
港未強制標籤基因食品
明報
國際要聞 A24
英國首次成功複製人類胚胎
成報
國際要聞 A19
改造病毒基因治療天花
蘋果日報
健康與醫療 A20
抗議基因玉米
大公報
科學 B07
轉基因食品 疑慮未息 古法耕種成增產新趨勢
成報
星期綠檔案 A14
稻米混人類基因 引發「人吃人」憂慮
都市日報
國際 P10
日培植人類基因米 被轟科學怪人食物
蘋果日報
國際新聞 A29
港大型米商不進口基因米
明報
輕 zone 特區 A20
綠色和平促標轉基因成份
文匯報
重要新聞 A06
更改基因能改變個人特徵
蘋果日報
國際要聞 A17
基因療法治愛滋大突破
東方日報
兩岸 A09
化石藏細胞軟組織 複製恐龍有望
太陽報
國際新聞 A20
全球基因改造農田增兩成
明報
輕 zone 特區 A23
政府擬訂基因食品標籤指引
太陽報
本地新聞 A32
複製小牛新法
明報
國際 A31
發現沙士異常 RNA
蘋果日報
國際頭條 A25
含人類激素基因牛誕生
星島日報
國際 A20
人類 16 號染色體揭秘 含癌症基因助醫療研究
太陽報
國際新聞 A18
植物基因改造可防禽流
成報
港聞 A08
非基因改造可放心吃
蘋果日報
中國新聞 A28
簡悅威基因斷症之父 《邵逸夫獎》之《基因探索
香港經濟日報 影視樂 C19
者》
Date
2005-08-25
2005-08-23
2005-08-23
2005-08-21
2005-08-14
2005-08-12
2005-08-08
2005-08-06
2005-08-04
2005-08-04
2005-07-27
2005-07-26
2005-07-26
2005-07-24
2005-07-01
2005-06-29
2005-06-24
2005-06-15
2005-06-07
2005-05-24
2005-05-24
2005-05-23
2005-05-23
2005-05-23
2005-05-21
2005-05-19
2005-05-08
2005-04-30
2005-04-26
2005-04-25
2005-04-14
2005-04-09
2005-04-05
2005-03-27
2005-03-26
2005-03-17
2005-03-03
2005-02-18
2004-12-29
2004-12-26
2004-12-25
2004-10-03
2004-09-14
2004-08-28
15
Trial Version
Glossary
English
Autism
Autosomal
Bacteriophage
Biotechnology
Chromosomes
Denaturation
Deoxyribonucleic acid
Diabetics
DNA Fingerprinting
Enzyme
Ethanol
Fermentation
Gene Cloning
Gene therapy
Genes
Genetic Engineering
Genetic research
Hemophilia
Hepatitis B vaccine
Herbicide
Inflammation
Inheritance
Mendelian
Mutation
Nucleic acid
Parkinson’s disease
Pesticide
Replication
Ribonucleic acid
Sickle cell anemia
Slaughterhouses
Trait
Chinese
孤獨症
常染色體的
噬菌體
生物工程學
染色體
改變本質
去氧核糖核酸(簡稱 DNA)
糖尿病
DNA 指紋術
酵
乙醇,酒精
發酵
基因複製
基因治療
遺傳因子
遺傳工程
基因研究
血友病
B 型肝炎疫苗
除草劑
發炎
遺傳
孟德爾遺傳定律的
變種
核酸
帕金森氏病
殺蟲劑
複製
核醣核酸
鐮狀細胞性貧血
屠殺場
特徵
16