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BIOTECHNOLOGY
DNA Technology
On November 22, 1983, the sleepy English village of Narborough awoke to news of a horrific crime: A
15-year-old-girl named Lynda Mann had been raped and murdered on a country lane near her home.
The killer left behind few clues, except for semen on the victim’s body and clothes. Despite extensive
investigation, the trail of evidence ran cold and the crime went unsolved. Three years later, the horror
resurfaced when another 15-year old girl, Dawn Ashworth, was also raped and murdered less than a
mile away from the first crime scene. When tests indicated that the 1983 and 1986 semen samples
could be from the same man, police began to search for a double murderer. After another extensive
investigation, a maintenance worker from a nearby hospital was arrested and charged with both crimes.
Under considerable pressure from police, the worker confessed to the second murder, but denied
committing the first.
In an attempt to pin both murders on the suspect, investigators turned to Alec Jeffreys, a professor at
nearby Leicester University, who had recently developed the first DNA fingerprint identification
system. Because the DNA sequence of every person unique (except for identical twins), DNA
fingerprinting can be used to determine with near certainty whether two samples of genetic material are
from the same individual. Jeffreys compared DNA from the 1983 and 1986 semen samples. As the
police suspected, the DNA analysis proved that the same person had committed both crimes. However,
when Jeffreys analyzed the suspect’s DNA, it did not match either crime scene sample, proving that the
suspect must he innocent. The police quickly released the suspect, making him the first person in legal
history to be exonerated by DNA evidence.
The detectives were back at square one. In an attempt to collect more evidence, they asked every young
male from the surrounding area to donate blood for DNA testing. Although 5,000 men were sampled,
none had DNA that matched the evidence from the crime scenes. The police were once again stymied.
The case finally broke when a pub-goer described how a man named Cohn Pitchfork had bullied him
into submitting blood on Pitchfork’s behalf. The police promptly arrested Pitchfork and took a sample
of his blood. Indeed, his DNA matched the samples from the two crime scenes. Cohn Pitchfork pleaded
guilty to both crimes, closing the first murder case ever to be solved by DNA evidence.
The Narborough murders were the first of many criminal investigations that have relied on DNA
evidence. DNA technology— methods for studying and manipulating genetic material—have rapidly
revolutionized the field of forensics, the scientific analysis of evidence for legal investigations. Since
its introduction, DNA fingerprinting has become a standard law enforcement tool and has provided
crucial evidence (of both innocence and guilt) in many famous cases, including the O.J. Simpson murder trial and the impeachment of President Bill Clinton. As we will see, DNA technology has
applications in many other fields, from cancer research to agriculture and even history. Perhaps the
most exciting use of DNA technology in basic research is the Human Genome Project, whose goal was
to map the entire human DNA down to the level of its nucleotide sequences. This project is expected to
help us better understand and treat many diseases.
There are several significant roles that DNA technology has assumed in society, including gene cloning
to produce useful products, DNA fingerprinting and forensic science, human gene therapy for the
treatment of disease, comparisons of genomes from different organisms, and the agricultural production
of genetically modified organisms. There are also some of the social, legal, and ethical issues that are
raised by these new technologies.
Biotechnology Products From Bacteria
The use of technology to alter the genomes of viruses, bacteria, and other cells for medical or
industrial purposes is called genetic engineering. These days, bacteria, plants, and animals are
genetically engineered to produce biotechnology products. Organisms that have had a foreign gene
inserted into them are called transgenic organisms. (TRANSferred GENE = TRANS GENIC)
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DNA technology is changing the pharmaceutical industry and medicine
DNA technology, and gene cloning in particular, is widely used to produce medicines and to diagnose
diseases.
Therapeutic Hormones Consider human insulin and human growth hormone (HGH). In the United
States alone, about 2 million people with diabetes depend on insulin treatment. Before 1982, the main
sources of this hormone were pig and cattle tissues obtained from slaughterhouses. Insulin extracted
from these animals is chemically similar, but not identical, to human insulin, and it causes harmful side
effects in some people. Genetic engineering has largely solved this problem by developing bacteria that
synthesize and secrete actual human insulin. In 1982, Human growth hormone was harder to produce
than insulin because the HGH molecule is about twice as big. Because growth hormones from other
animals are not effective in humans HGH was urgently needed. In 1985, molecular biologists made an
artificial gene for HGH by joining a human DNA fragment to a chemically synthesized piece of DNA;
using this gene, they were able to produce HGH in E. coil. Before this genetically engineered hormone
became available, children with a HGH deficiency had to rely on scarce supplies from human cadavers
or else face dwarfism.
Human insulin produced by bacteria
In 1982, Humulin became the first recombinant drug approved by the Food and Drug Administration
Biotechnology Products From Bacteria
Recombinant DNA technology means to recombine the DNA of an organism to make it more useful to
humans. It is used to produce bacteria that reproduce in large vats to get them to make a large amount
of a particular protein, such as insulin, growth hormone, clotting proteins for hemophiliacs, and
hepatitis B vaccine.
DNA technology is also helping medical researchers develop vaccines.
• A vaccine is a harmless variant or derivative of a pathogen (usually a bacterium or virus) that is
used to prevent an infectious disease.
• When a person is inoculated, the vaccine stimulates the immune system to develop lasting defenses against the pathogen.
• For the many viral diseases for which there is no effective drug treatment, prevention by vaccination is virtually the only medical way to prevent illness.
• One DNA technology vaccine is for the hepatitis B virus.
• Hepatitis is a disabling and sometimes fatal liver disease, and the hepatitis B virus may also
cause liver cancer.
• Smallpox was once a dreaded human disease, but it was eradicated worldwide in the 1970s by
widespread vaccination with a harmless variant of the smallpox virus.
• In fact, the harmless virus could be engineered to carry the genes needed to vaccinate against
several diseases simultaneously.
• In the future, one inoculation may prevent a dozen diseases.
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Biotechnology Products From Bacteria that help plants
Transgenic bacteria can also help plants.
For example, bacteria that live in plants have genes spliced in that let them resist insect toxins; this
protects the roots of the plants, too.
Bacteria can be genetically engineered to degrade a particular substance, for instance, transgenic
bacteria have been produced which have the ability to eat oil after an oil spill. Industry has found
that bacteria can be used as filters to prevent airborne chemicals from being vented into the air. They
can also remove sulfur from coal before it is burned and help clean up toxic dumps. Furthermore, these
bacteria were given “suicide” genes that cause them to self-destruct when the job is accomplished.
Many major mining companies already use bacteria to obtain various metals.
Genetic engineering may enhance ability of bacteria to extract copper, uranium, and gold.
Biotechnology Products From Plants
Plants can also be genetically engineered to make cotton, corn, soybeans, and potatoes resistant to pests
because their cells now produce an insect toxin.
Plants are also being engineered to produce human hormones, clotting factors, and antibodies, in
their seeds. One type of antibody made by corn can deliver a substance that kills tumor cells, and
another made by soybeans can be used as treatment for genital herpes.
Genetically modified organisms are transforming agriculture
Scientists concerned with feeding the growing human population are using DNA technology to make
genetically modified (GM) organisms for use in agriculture. A GM organism (Or GMO) is one that has
acquired one or more genes by artificial means rather than by traditional breeding methods. (The new
gene may or may not be from another species.)
To make genetically modified plants, researchers can manipulate the DNA of a single cell and then
grow a plant with a new trait from the engineered cell. Already in commercial use are a number of crop
plants carrying new genes for desirable traits, such as delayed ripening and resistance to spoilage and
disease.
The most common vector used to introduce new genes into plant cells is a piece of DNA from a soil
bacterium. With the help of a special enzyme, the gene for the desired trait is inserted into a plant cell,
where it is integrated into a plant chromosome. Finally, the recombinant cell is cultured and grows into
a whole plant. If the newly acquired gene is from another species, the recombinant organism is called a
transgenic organism.
Genetic engineering is rapidly replacing traditional plant-breeding programs, especially in cases where
useful traits are determined by one or only a few genes. For example, the majority of the American
soybean and cotton crops are genetically modified. Many of these GM plants have received bacterial
genes that make the plants resistant to herbicides or pests. Farmers can more easily grow these crops
with far less tillage and reduced use of chemical insecticides.
Genetic engineering also has great potential for improving the nutritional value of crop plants. “Golden
rice,” a transgenic variety with a few daffodil genes, produces grains containing beta-carotene, which
our body uses to make vitamin A. This rice could help prevent vitamin A deficiency—and resulting
blindness—among the half of the world’s people who depend on rice as their staple food.
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Biotechnology Products From Animals
Agricultural researchers are also making transgenic animals. To do this, scientists first remove egg cells
from a female and fertilize them in vitro. They then inject a previously cloned gene directly into the
nuclei of the fertilized eggs. Some of the cells integrate the foreign DNA into their genomes. The
engineered embryos are then surgically implanted in a surrogate mother. If an embryo develops
successfully, the result is a transgenic animal, containing a gene from a third “parent” that may even be
of another species.
Techniques have been developed to insert genes into the eggs of animals. The procedure has been used
to produce larger fish, cows, pigs, rabbits, and sheep. Genetically engineered fishes are now being kept
in ponds that offer no escape to the wild because there is much concern that they will upset or destroy
natural ecosystems.
The goals of creating a transgenic animal are often the same as the goals of traditional breeding—for
instance, to make a sheep with better quality wool or a cow that will mature in a shorter time. Scientists
might, for example, identify and clone a gene that causes the development of larger muscles (muscles
make up most of the meat we eat) in one variety of cattle and transfer it to other cattle or even to sheep.
Transgenic animals also have been engineered to be pharmaceutical “factories” that produce otherwise
rare biological substance for medical use. Recently, researchers have engineered transgenic chickens
that express large amounts of the foreign product in their eggs. This success suggests that transgenic
chickens may emerge as relatively inexpensive pharmaceutical factories in the near future.
Gene pharming is the use of transgenic farm animals to produce therapeutic drugs in the
animal’s milk. There are plans to produce drugs for the treatment of cystic fibrosis, cancer, blood
diseases, and other disorders. An anti-clotting medicine is currently being produced by a herd of goats.
Animals have been engineered to produce growth hormone in their urine instead of in milk. Urine is
preferable to milk because only females produce milk, and not until maturity, but all animals produce
urine from birth.
Xenotransplantation
Scientists have begun the process of genetically engineering animals to serve as organ donors for
humans who need a transplant. We now have the ability to transplant kidneys, heart, liver, pancreas,
lung, and other organs. Unfortunately, however, there are not enough human donors to go round. Fifty
thousand Americans need transplants a year, but only 20,000 patients get them. As many as 4,000 die
each year while waiting for an organ. You might think that apes, such as the chimpanzee or the baboon
might be a scientifically suitable species for this purpose. But apes are slow breeders and many people
object to using apes for this purpose. In contrast, pigs have been an acceptable meat source, and a
female pig can become pregnant at six months and can have two litters a year, each averaging about ten
offspring. Ordinarily, the human body rejects transplanted pig organs. Genetic engineering, however,
can make pig organs good for transplantation at less of a rejection risk.
Cloning of Animals
Imagine that an animal has been genetically altered to serve as an organ donor. What would be the best
possible way to get identical copies of this animal? If cloning of the animal was possible, you could get
many exact copies of this animal. Cloning is a form of asexual reproduction (without sex) because
it requires only the genes of that one animal. In 1997, scientists at the Raslin institute in Scotland
announced that they produced a cloned sheep called Dolly. In 1998, genetically altered calves were
cloned in the United States using the same method.
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Could GM organisms harm human health or the environment?
As soon as scientists realized the power of DNA technology, they began to worry about potential
dangers. Early concerns focused on the possibility that recombinant DNA technology might create new
pathogens. What might happen, for instance, it cancer cell genes were transferred into bacteria or
viruses?
To guard against such rogue microbes, scientists developed a set of guidelines that were adopted as
formal government regulations in the United States and some other countries. One safety measure is a
set of strict laboratory procedures designed to protect researchers from infection by engineered
microbes and to prevent the microbes from accidentally leaving the laboratory. In addition, strains of
microorganisms to be used in recombinant DNA experiments are genetically crippled to ensure that
they cannot survive outside the laboratory. Finally, certain obviously dangerous experiments have been
banned.
Today, most public concern about possible hazards centers not on recombinant microbes but on
genetically modified (GM) crop plants. Advocates of a cautious approach fear that some crops carrying
genes from other species might cause allergies in humans or create super-weeds that are hazardous to
the environment.
Today, governments and regulatory agencies throughout the world are grappling with how to facilitate
the use of biotechnology in agriculture, industry, and medicine while ensuring that new products and
procedures are safe. In the United States, all projects are evaluated for potential risks by regulatory
agencies such as the Food and Drug Administration, Environmental Protection Agency, National
Institutes of Health, and Department of Agriculture. These agencies are under increasing pressure from
some consumer groups.
The Human Genome Project
The Human Genome Project was a massive effort to put all of the genes in human chromosomes
into the proper sequence. This was just finished in 2003.
Project goals were to identify all the 25,000 genes in human DNA and determine the sequences of the 3
billion amino acids that make up human DNA. This allows scientists to detect some defective genes
and tailor a treatment plan to the individual.
Gene Therapy
For example, there is a genetic disease of the liver that causes it to malfunction and leads to high levels
of blood cholesterol, which makes the patient subject to fatal heart attacks at a young age. The person is
injected with a virus that contains the normal gene. Another example is when fat enzymes are coated
with the missing gene to cure cystic fibrosis and then sprayed into patients’ nostrils. Anti-cancer genes
can also be injected directly into cancerous tumors. Perhaps it will be possible also to use gene therapy
to cure hemophilia, diabetes, Parkinson disease, or AIDS.
Diagnosis and Treatment of Disease
DNA technology is being used increasingly in disease diagnosis. It is used to determine which genes are associated
with genetic diseases. An individual’s gene expression profile may someday allow physicians to tailor treatments for
many different disorders.
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The Role of Recombinant DNA technology in Biotechnology
Recombinant DNA technology
Intentionally modifying genomes of organisms for practical purposes
Three goals
Eliminate undesirable phenotypic traits
Combine beneficial traits of two or more organisms
Create organisms that synthesize products humans need
The Tools of Recombinant DNA Technology
Mutagens
Physical and chemical agents that produce mutations
Scientists utilize mutagens to
Create changes in microbes’ genomes to change phenotypes
Select for and culture cells with beneficial characteristics
Mutated genes alone can be isolated
The Use of Reverse Transcriptase to Synthesize cDNA
Isolated from retroviruses
Uses RNA template to transcribe molecule of DNA
Easier to isolate mRNA molecule for desired protein first
Allows cloning in prokaryotic cells
Synthetic Nucleic Acids
Molecules of DNA and RNA produced in cell-free solutions
Uses of synthetic nucleic acids
Elucidating the genetic code
Creating genes for specific proteins
Synthesizing DNA and RNA probes to locate specific sequences of nucleotides
Synthesizing antisense nucleic acid molecules
Restriction Enzymes
Bacterial enzymes that cut DNA molecules only at restriction sites
One enzyme might only cleave T-T apart; another enzyme only cleaves A-T apart, etc.
We use one enzyme, and see how many pieces result. Then we use the next enzyme, etc. That shows us
the sequence of DNA in a sample.
Vectors
Nucleic acid molecules that deliver a gene into a cell
Useful properties
Small enough to manipulate in a lab
Survive inside cells
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Contain recognizable genetic marker
Ensure genetic expression of gene
Include viral genomes, transposons, and plasmids
Gene Libraries
A collection of bacterial or phage clones
Each clone in library often contains one gene of an organism’s genome
Library may contain all genes of a single chromosome
Library may contain set of DNA complementary to mRNA
Techniques of Recombinant DNA Technology
Multiplying DNA in vitro: The Polymerase Chain Reaction (PCR)
Large number of identical molecules of DNA produced in vitro
Critical to amplify DNA in variety of situations
Epidemiologists use to amplify genome of unknown pathogen
Amplified DNA from Bacillus anthracis spores in 2001 to identify source of spores
Repetitive process consisting of three steps
Denaturation
Priming
Extension
Can be automated using a thermocycler
Separating DNA Molecules: Gel Electrophoresis and the Southern Blot
Gel electrophoresis
Separates molecules based on electrical charge, size, and shape
Allows scientists to isolate DNA of interest
Negatively charged DNA drawn toward positive electrode
Agarose makes up gel; acts as molecular sieve
Smaller fragments migrate faster and farther than larger ones
Determine size by comparing distance migrated to standards
Techniques of Recombinant DNA Technology
Separating DNA Molecules: Gel Electrophoresis and the Southern Blot
Southern blot
DNA transferred from gel to nitrocellulose membrane
Probes used to localize DNA sequence of interest
Northern blot – used to detect RNA
Uses of Southern blots
Genetic “fingerprinting”
Diagnosis of infectious disease
Demonstrate incidence and prevalence of organisms that cannot be cultured
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DNA Microarrays
Consist of molecules of immobilized single- stranded DNA
Fluorescently labeled DNA washed over array will adhere only at locations where there are
complementary DNA sequences
Variety of scientific uses of DNA microarrays
Monitoring gene expression
Diagnosis of infection
Identification of organisms in an environmental sample
Inserting DNA into Cells
Goal of DNA technology is insertion of DNA into cell
Natural methods
Transformation
Transduction
Conjugation
Artificial methods
Electroporation
Protoplast fusion
Injection – gene gun and microinjection
Transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and
expression of exogenous DNA from its surroundings. Transformation occurs naturally in some species
of bacteria, but it can also be caused artificially.
Transduction is when DNA is transferred from one bacterium to another by a virus (bacteriophage).
Conjugation is when a bacterium uses its sex pilus to transfer some of its DNA to another bacterium.
Applications of Recombinant DNA Technology
Genetic Mapping
Locating genes on a nucleic acid molecule
Provides useful facts concerning metabolism, growth characteristics, and relatedness to others
Locating Genes
Until 1970, genes identified by labor-intensive methods; Simpler and universal methods now available
Restriction fragmentation
Fluorescent in situ hybridization (FISH)
Used to detect and localize the presence or absence of specific DNA sequences on
chromosomes. Also allows for more precise DNA karyotyping.
Environmental Studies
Most microorganisms have never been grown in a laboratory
Scientists know them only by their DNA fingerprints
Allowed identification of over 500 species of bacteria from human mouths
Determined that methane-producing archaea are a problem in rice agriculture
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Pharmaceutical and Therapeutic Applications
Protein synthesis
Creation of synthetic peptides for cloning
Vaccines
Production of safer vaccines
Introduce genes of pathogens into common fruits and vegetables
Injecting humans with plasmid carrying gene from pathogen
Humans synthesize pathogen’s proteins
Genetic screening
DNA microarrays used to screen individuals for inherited disease caused by mutations
Can also identify pathogen’s DNA in blood or tissues
DNA fingerprinting
Identifying individuals or organisms by their unique DNA sequence
Gene therapy
Missing or defective genes replaced with normal copies
Some patients’ immune systems react negatively
Medical diagnosis
Patient specimens can be examined for presence of gene sequences unique to certain pathogens
Xenotransplants: Animal cells, tissues, or organs introduced into human body
DNA technology is used in courts of law
DNA technology plays an important role in forensic science, the scientific analysis of evidence for
crime scene and other legal investigations. In violent crimes, body fluids or small pieces of tissue may
be left at the crime scene or on the clothes of the victim or assailant; if rape has occurred, semen may
be recovered from the victim’s body. With enough tissue or semen, forensic scientists can determine the
blood type or tissue type using older methods that test for proteins. However, such tests require fresh
samples in relative large amounts. Also, because many people have the same blood or tissue type, this
approach can only exclude a suspect; it cannot provide strong evidence of guilt.
DNA testing, on the other hand, can identify the guilty individual with a high degree of certainty
because the DNA sequence of every person is unique (except for identical twins). DNA testing requires
only about 1,000 cells. In a murder case, for example, such analysis can be used to compare DNA
samples from the suspect, the victim, and bloodstains on the suspect’s clothes. They provide a DNA
fingerprint, or specific pattern of bands.
DNA fingerprinting can also be used to establish family relationships. A comparison of the DNA of a
mother, her child, and the purported father can conclusively settle a question of paternity. Sometimes
paternity is of historical interest: DNA fingerprinting provided strong evidence that Thomas Jefferson
or one of his close male relatives fathered at least one child with his slave Sally Hemings.
Just how reliable is DNA fingerprinting? In most legal cases, the probability of two people having
identical DNA fingerprints is between one chance in 100,000 and one in a billion. For this reason, DNA
fingerprints are now accepted as compelling evidence by legal experts and scientists alike. In fact,
DNA analysis on stored forensic samples has provided the evidence needed to solve many “cold cases”
in recent years. DNA fingerprinting has also exonerated many wrongly convicted people, some of
whom were on death row.
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DNA Fingerprinting and the Criminal Justice System
Traditional fingerprinting has been used for years to identify criminals and to exonerate those wrongly
accused of crimes. The opportunity now arises to use DNA fingerprinting in the same way. DNA
fingerprinting requires only a small DNA sample. This sample and calm from blood left at the scene of
a crime, semen from a rape case, even a single hair root!
The DNA is amplified, cut with restriction enzymes, and separated by gel electrophoresis to produce a
unique DNA fragment pattern. The same procedure is done several times with restriction enzymes,
making it nearly impossible for anyone else in the world would have the same set of patterns.
Advocates of DNA fingerprinting claim that identification is beyond a reasonable doubt.
Opponents of this technology, however, point out that it is not without its problems. Police or
laboratory negligence can invalidate the evidence. For example, during the O.J. Simpson trial, the
defense claimed that the DNA evidence was inadmissible because it could not be proven that the police
had not planted over Jay's blood at the crime scene. There have also been reported problems with
sloppy laboratory procedures and the credibility of forensic experts. In addition to identifying
criminals, DNA fingerprinting can be used to establish paternity and maternity, determine nationality
for immigration purposes, and identify victims of a national disaster, such as the terrorist attack of
September 11, 2001.
Considering the usefulness of DNA fingerprints, perhaps everyone should be required to contribute
blood to create a national DNA fingerprint data bank. Some say however this would constitute an
unreasonable search, which is unconstitutional.
1. Would you be willing to provide your DNA for a national DNA data bank? What types of privacy restrictions would you want on your DNA?
2. If not everyone, do you think that convicted felons at least should be required to provide DNA
for a databank?
3. Should all defendants have access to DNA fingerprinting (at government expense) to prove that
they did not do a crime? Should this include those already convicted of crimes who want to reopen their cases using new DNA evidence?
Agricultural Applications
Production of transgenic organisms
Recombinant plants and animals altered by addition of genes from other organisms
Herbicide resistance
Gene from Salmonella conveys resistance to glyphosate (Roundup)
Farmers can kill weeds without killing crops
Salt tolerance
Scientists have removed gene for salt tolerance and inserted into tomato and canola plants
Transgenic plants survive, produce fruit, and remove salt from soil
Freeze resistance
Crops sprayed with genetically modified bacteria can tolerate mild freezes
Pest resistance
Bt toxin
Naturally occurring toxin only harmful to insects
Organic farmers used to reduce insect damage to crops
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Gene for Bt toxin inserted into various crop plants
Genes for Phytophthora resistance inserted into potato crops
Improvements in nutritional value and yield
Tomatoes allowed to ripen on vine and shelf life increased
Gene for enzyme that breaks down pectin suppressed
BGH allows cattle to gain weight more rapidly,
Have meat with lower fat content and produce 10% more milk
Gene for β -carotene (vitamin A precursor) inserted into rice
Scientists considering transplanting genes coding for entire metabolic pathways
The Ethics and Safety of Recombinant DNA Technology
Supremacist view – humans are of greater value than animals
Long-term effects of transgenic manipulations are unknown
Unforeseen problems arise from every new technology and procedure
Natural genetic transfer could deliver genes from transgenic plants and animals into other organisms
Transgenic organisms could trigger allergies or cause harmless organisms to become pathogenic
Studies have not shown any risks to human health or environment
Standards imposed on labs involved in recombinant DNA technology
Can create biological weapons using same technology
Ethical Issues
Routine screenings?
Who should pay?
Genetic privacy rights?
Profits from genetically altered organisms?
Required genetic screening?
Forced correction of “genetic abnormalities”?
Are Genetically Engineered Foods Safe?
A series of focus groups conducted by the Food and Drug Administration in 2000 showed that although
most participants believed that genetically engineered foods might offer benefits, they also feared
unknown long-term health consequences that might be associated with the technology. Some say that
when it comes to human and environmental safety, there should be clear evidence of the absence of
risks.
The discovery that a genetically engineered corn called Star Link had inadvertently made it into the food
supply triggered the recall of chocolate shells, tortillas, and many other corn-based foodstuffs from
supermarkets. Further, the makers of Star Link were forced to buy back Star Link from farmers and to
compensate food producers at an estimated cost of several hundred million dollars. Star Link is a type of
corn that contains a foreign gene taken from a common soil bacterium whose insecticidal properties have
long been known. About a dozen varieties of this corn, as well as potatoes and one variety of tomato, have
now been approved for human consumption. These strains contain a gene for an insecticidal protein. The
makers of Star Link decided to use a gene for a related protein. They thought that using this molecule might
slow down the chances of pest resistance to the genetically modified corn. In order to get FDA approval for
use in foods, the makers of Star Link performed the required tasks. Like the other now approved strains, star
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Linked was not poisonous to rodents, and its biochemical structure is not similar to those of most food
allergens. However, it resisted digestion and longer than the other genetically modified proteins when it was
put in simulated stomach acid and subjected to heat. Because most food allergens are stable like this, star
Linked was not approved for human consumption.
The scientific community is now trying to devise more tests for allergens because it has not been possible to
determine conclusively whether or not this second protein is an allergen. It is also unclear how resistant to
digestion of protein must be in order to be an allergen, and it is also unclear what degree of sequence
similarity a potential allergen must have two unknown allergy and to raise concern. Therefore, it is not
understood yet where the thresholds are for sensitization to food allergens and thresholds for the visitation of
a reaction with food allergens.
Other scientists are concerned about the following potential drawbacks to planting this variety of
genetically modified corn: resistance among populations of the target past, exchange of genetic
material between the transgenic crop and related plant species, and crops impact on non-target species.
They feel that many more studies are needed before it can be said for certain that genetically modified
corn has no ecological drawbacks.
Despite controversies, the planting of genetically engineered corn increased in 2001. The USDA
reports that US armors planted genetically engineered corn on 26% of all corn acres, 1% more than in
2000. In all, US farmers planted at least 72 million acres with mostly genetically engineered corn,
soybeans, and cotton. The public wants all of genetically engineered foods to be labeled as such, but
this may not be easy to accomplish because most corn meal is derived from both conventional and
genetically engineered corn. So far, there has been no attempt to sort out one type of food product from
the other.
Genetic Profiling
Now that the human genome has been sequenced, researchers are using various means to discover
which sequencing differences among people might forecast the possibility of a future disease. No
doubt, there are benefits to genetic profiling. For example, knowledge of your genes might indicate
your susceptibility to various types of cancer. This information could be used to develop a prevention
program, including the avoidance of environmental influences associated with the disease. Also, you
would be less inclined to smoke if you knew your genes make it almost inevitable that smoking will
give you lung cancer. Are there any reasons not to be in favor of genetic profiling?
People, however, worry that insurance companies and employers could use their genetic profile against
them. Perhaps employers will not higher, or insurance companies will not ensure, those who have a
propensity for particular diseases. The federal government and about 25 states have passed laws
prohibiting genetic discrimination by health insurers, and 11 have passed laws prohibiting genetic
discrimination by employers. The legislation states that genetic information cannot be released to
anyone without the subject’s permission. Is that such legislation enough to ally are fears of
discrimination? Might an employer not hire you or an insurance company not ensure you simply
because you will not grant permission to access your genetic profile?
Say that two women are being considered for the same position, and each meets all the basic
requirements for the job. The first denies access to her genetic profile, while the second one grants
permission to look at her genetic profile. Thinking that the first woman might have had something to
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hide, employer hires a second one. The possibility that sick days may be needed by the first woman
makes the second woman a more cost-effective choice. People who have genetic profiles proving they
are likely to be healthy in the future might even use them in order to have an advantage over those who
have profile showing that they are likely to develop serious illnesses in the future. In this way, we
might create a genetic underclass.
Genetic information is sometimes misunderstood, particularly by laypeople. In the past, for example,
as an effort to combat sickle cell disease, many people were screened for it. Unfortunately, those who
were found to have the sickle trait, and not the actual disease, experienced discrimination at school, or
from employers and insurance carriers. It is possible misunderstanding of the results enough not to do
genetic profiling, or do the potential benefits outweigh the risks?
On the other hand, employers may fear that the government might use genetic information one day to
require them to provide an environment specific to every employee's need, in order to prevent future
illness. Would you approve of this, or should individuals be required to leave an area or job that
exposes them to an environmental influence that could be detrimental to their health?
Some people believe that free access to genetic profiling data is absolutely essential to developing
better preventative care for all. If researchers can match genetic profiles to the environmental
conditions that bring on illnesses, they could come up with better prevention guidelines for the next
generation. Should genetic profiles and health records become public information under these
circumstances? It would particularly help in the study of complex diseases, such as cardiovascular
disorders, non-insulin-dependent diabetes, and juvenile rheumatoid arthritis. Perhaps there would be
some way to protect privacy and still make the information known?
If present legislation to protect privacy is inadequate, what can be done to truly keep such information
private? Should the information be coded in some way, so that only the medical profession can read it?
Should people be responsible for keeping the only copy of their profiles, which would be coded so that
even they cannot read it? Or, do you believe that anyone should have access to anyone's profile, for
whatever reason?
1. Should people be encouraged or even required to have their DNA analyzed so that they can develop programs to possibly prevent future illness?
2. Should employers be encouraged or required to provide an environment suitable to a person's
genetic profile? Or should the individual ovoid a work environment that could bring on an illness?
3. How come we balance individual rights with the public health benefits of matching genetic profiles to detrimental environments?
Medicine’s Wild Kingdom Time Magazine
Potent chemicals derived from exotic animals are yielding a range of treatments.
One creature you don't want to stumble upon it in a dark forest is a hungry vampire bat. The 3 inch
long, pointy eared night stalker has an anti-clotting substance and its saliva that allows it to dine on an
unending flow of its victim’s blood. There is, however, one group of people that may come to see the
vampire bats as lifesavers. They are stroke patients to desperately need improved clot-busting drugs
that prevent brain damage and paralysis by restoring blood flow to stroke ravaged tissues.
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That's the idea behind a new drug that 15 US hospitals will soon begin testing. It's a synthetic copy of
an enzyme bats secrete when they salivate over freshly bitten gray. Stroke experts are already buzzing
because early studies in mice suggests patients may be able to safely receive the bat spit up to nine
hours after they've had a stroke. The only clot-busting drug now on the market must be given within
three hours.
Bats are not the only scary animals that may someday contribute to the world's expanding medicine
cabinet. Scientists are studying everything from Gila monsters to scorpions to copperhead snakes. The
toxins these creatures use to kill their prey or ward off foes hold seemingly boundless potential to treat
human diseases ranging from diabetes to brain cancer. Refined through millions of years of evolution,
these substances found in animal saliva, then um, and, in some internal organs homed in on targets such
as nerve cells better than most chemical combination's scientists concoct. And often they circulate in
the body for hours on end.
Still, turning Mother Nature’s toxins into life-saving drugs can be harder than killing a Python with a
pebble. First, researchers must isolate, analyze, and synthesize specific compounds in such a way that
they can be tolerated by humans and mass produced. The risk of failure is so high that many
pharmaceutical companies shun poison derived experimental drugs until they are well past the
developmental stage. That leaves scientists dependent upon scarce venture capital and public funding.
Scientists are also racing against a biological clock. Species identified to date may represent just 1/10
of the biological diversity on earth. And potentially therapeutic creatures are vanishing at
unprecedented rates. Although the vampire bat is not endangered, 13 other bat species are. The natural
world is the largest pharmaceutical factory we have, and a lot of potential benefit is being lost.
Drugs like the synthesized bat spit can earn attractive returns. An anticoagulant derived from leach
saliva pulled in an estimated $38 million last year. And a hypertension drug derived from the venom of
the South American viper drew more than $1 billion in annual sales before the compounds became
available in generic form in the mid-1990s.
Many animal poisons have the ability to hit specific bull’s-eyes in the body. One species of snail, for
example, injects its prey with a poison that paralyzes nerve cells. The tiny Ecuadorian Poison Dart
Frog secretes a skin toxin that keeps predators at bay. Both substances block pain signals to the brain
and have led to experimental pain medications that could be as potent as morphine but with no risk of
addiction. The poison in puffer fish has also been found to ease the pain of heroin withdrawal and
cancer.
For sheer horror, nothing matches staining of the 8 inch giant yellow Israel scorpion. It packs
neurotoxins that can cause excruciating pain. Yet at least one of the hundreds of proteins involved in
that process also has the ability to seek out and find to a receptor that is abnormally expressed on the
surface of brain tumor cells but not on normal selves.
Last year, to cancer centers began testing a copy of the protein that was developed from this toxin. The
researchers compared the synthesized protein with a radioactive isotope and injected it into the brains
of clinical trial patients suffering from a cancer called glioma. In the brain, they believe, the drug
travels straight to the tumors and kills them without damaging nearby healthy cells. It's like a guided
missile.
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Exotic animals and their secretions don't necessarily have to be lethal to help humans. One
pharmaceutical company hopes to obtain food and drug administration approval for a diabetes drug
derived from a hormone that Gila monsters secrete while munching on mice, bird eggs, and other
favorite foods. This substance mimics the human hormone that regulates insulin, which in turn
controls blood sugar. But unlike the human molecule, which is quickly degraded by enzymes in the
body, the lizard version sticks around for hours. And it helps the body regenerate insulin making cells.
This can take us to new levels of blood sugar control.
Despite the promise of animal-based drugs, the path from the rain forest to the FDA is rough with
pitfalls. For many companies, the biggest challenge has been figuring out how to develop and produce
chemical copies of naturally occurring substances. A professor at the University of Southern California
School of medicine in has been developing a cancer drug based on the venom of the Southern
copperhead snake. With a shoestring budget from public grants, he managed to coax mammalian cells
to make copies of the venom protein. But it will be at least a year before a drug is ready for human
testing.
Emerging technologies should help speed the discovery and development of exotic drugs.
Computerized screening systems, for example, allow researchers to test experimental compounds
against thousands of potential disease targets simultaneously. That's important because science has
barely scratched the surface of nature’s therapeutic potential. There are 10 million organisms out there
waging chemical warfare against each other; the abundance of possible drugs cannot even be imagined.
The problem is that many of these potential remedies are disappearing before they are even spotted.
Half of the world's plants and animals live in tropical forests, and most of these species are still
unknown. At the current rate of forest destruction, two thirds of land dwelling plant and animal species
will be extinct by the end of this century.
The urgency of preserving nature's bounty is not lost on patients like Duane Rualo. The 24-year-old
accounting student at Cal State Long Beach was diagnosed with glioma in late 2001 and told he
probably would not live long enough to make it to his fall 2003 graduation. After surgery and several
shots of scorpion venom, his latest brain scan came up clear of cancer. His doctors can't say yet how
important the scorpion has been to his recovery. But these days, Rualo pauses when he comes across a
scorpion exhibit at a zoo. “I stop and think:’ Wow, they may have saved my life’”, he says. And who
knows what other life-saving drugs may be lurking beyond the scorpions layer, the Gila monsters
burrow, and the bats caves?
New Cures on the Horizon
Now that we know the sequence of the bases in the DNA of all the human chromosomes, biologists all
over the world believe this knowledge will result in rapid medical advances for ourselves and our
children.
First prediction: Many new medicines tailored to the individual will be available.
Most drugs are proteins or small chemicals that are able to interact with proteins. Today's drugs were
usually discovered in a hit or miss fashion, but now researchers will be able to take a more systematic
approach to finding effective medicines. In a recent search for a menace and that makes wounds heal,
researchers cultured skin cells with 14 proteins that can cause skin cells to grow. Only one of these
proteins actually made skin cells grow and did nothing else. They expect this protein to become an
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effective drug for conditions such as venous ulcers, which are skin lesions that affect many thousands
of people in the United States. Tests leading to effective medicines can be carried out with many more
proteins that scientists will discover by examining the human genome.
Many drugs potentially have unwanted side effects. Why do some people and not others have won or
more of the side effects? Most likely, this is because people have different genetic profiles. It is
expected that a physician will be able to match patients to drugs that are safe or them on the basis of
their genetic profiles.
One study found that various combinations of mutations can lead to the development of asthma. A
particular medicine, called albuterol, is effective and safe for patients with certain combinations of
mutations and not others. This example and others showed that many diseases are multi-factorial and
that only a genetic profile is able to detect mutations are causing an individual to have a disease and
how it should be properly treated.
Second prediction: A longer and healthier life will be yours.
Pre-embryonic gene therapy may become routine once we discovered the genes that contribute to a
longer and healthier lives. We know that the presence of three radicals causes cellular molecules to
become unstable and cells to die. Certain genes are believed to code for antioxidant enzymes that
detoxify free radicals. It could be that human beings with particular forms of these genes have more
efficient antioxidant enzymes, and therefore live longer. If so, researchers will no doubt be able to
locate these genes and also others that promote a longer, healthier life. Perhaps certain genetic profiles
allow some people to live far beyond the normal lifespan. Researchers may be able to find which
genes allow individuals to live a long time and to make them available to the general public. Then,
many more people would live longer and healthier lives.
Third prediction: You will be able to design your children.
Genome sequence data will be used to identify many more mutant genes that cause genetic disorders
than are presently known. In the future, it may be possible to cure genetic disorders before the child is
born by adding a normal gene to any egg that carries a mutant gene. Or an artificial chromosome,
constructed to carry a large number of corrective genes, could automatically be placed in eggs. In vitro
fertilization would have to be utilized in order to take advantage of such measures for current genetic
disorders before conception.
Genome sequence data can also be used to identify genes for traits such as height, intelligence, or
behavioral characteristics. A couple could decide on their own which genes may wish to use to
enhance a child's phenotype. In other words, the sequencing of the human genome may bring about a
genetically just society, in which all types of genes would be accessible to all parents.
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