Transcript Chapter 10: Biotechnology

GENETIC ENGINEERING
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Genetic engineering is a process performed in a laboratory in which deliberate
changes are introduced into an individual’s genome.
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A gene from one species or even genus can be transferred into another species
(or genus), creating a transgenic organism.
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A gene from a species may also be removed, altered, and then re-inserted into
the same species.
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In either case, a genetically modified organism (GMO) is the result.
GENETICALLY MODIFIED MICROORGANISMS
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Bacteria and yeast are the most common GMOs.
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This is because they contain the metabolic “machinery” to produce desired
organic molecules (such as proteins), yet their DNA is easy to modify.
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Many bacteria and yeast have been modified to produce medically important
molecules.
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For example, since 1982, transgenic E. coli has been producing human insulin for
diabetics.
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Before this, diabetics had to use animal insulin and many suffered allergic
reactions.
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Slight gene modifications of the human insulin gene in E. coli has also allowed
scientists to produce both fast-acting and slow-release human insulin.
GENETICALLY MODIFIED MICROORGANISMS
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The food industry has also taken advantage of genetically modified microorganisms.
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Cheese traditionally produced using an extract from calf stomachs containing the
enzyme, chymotrypsin.
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Today, however, genetically modified bacteria produce this enzyme for use in cheesemaking.
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Other enzymes that are being produced by GMOs that are being used in the food
industry include enzymes that improve the taste and clarity of beer and fruit juices and
enzymes that slow the staling of bread.
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**Explain your own example of a genetically modified microorganism (bacterium,
yeast) that has not been discussed in this presentation or your textbook. What was the
purpose/benefit of creating this microorganism?
GENETICALLY MODIFIED MICROORGANISMS
Fluorescence microscopy image of bacteria which have been genetically engineered to produce the green
fluorescent protein. The amount of protein produced by each bacterium is under the control of a genetic circuit.
Mathematical analysis of naturally occurring circuits as well as the engineering of artificial gene circuits is a
rapidly expanding area of research at the interface of physics and biology.
Metabolix has already developed a process that uses genetically engineered yeast to produce plastics. DuPont has
developed a kind of bacteria that turns out polyesters. Several companies are developing organisms that will yield
larger quantities and higher concentrations of ethanol for automobile fuel.
DESIGNER PLANTS
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Plants can be genetically modified in several different ways.
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One way involves using the bacterium Agrobacterium tumefaciens.
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Agrobacterium tumefaciens is a bacterium that infects many plants including
peas, beans, potatoes, and other important food crops.
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Naturally, Agrobacterium tumefaciens carries a plasmid that causes tumors to
form on infected plants.
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However, scientists have genetically modified this plasmid by removing the tumorinducing gene and inserting desired genes.
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Then, a plant cell in infected with this modified bacterium. Whole plants can be
grown from these infected cells.
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The plants that are grown from these infected cells do not form tumors but,
instead, produce desired products such as natural pesticides that make the plant
more resistant to devastating plant diseases and pests.
DESIGNER PLANTS
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Genes can also be transferred into plants by electric or chemical shocks, or by
blasting the plant tissues with DNA-coated pellets.
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These genetically modified plants may also be engineered so that they have
double the yield of their unmodified counterparts.
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Some crops are also genetically modified so that they contain genes that make
them more resistant to environmental disturbances such as severe droughts like
those in Africa.
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**Explain your own example of a genetically modified plant that has not been
discussed in this presentation or your textbook. What was the purpose/benefit of
creating this plant?
WHY DESIGNER PLANTS?
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The human population is rapidly growing at a rate faster than food production can
keep up.
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Irrigation leaves mineral and salt residues in soils.
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Tilled soil erodes, allowing topsoil to be eroded away.
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Runoff clogs rivers and fertilizers on crops allows algae to overgrow so that it
suffocates fish.
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Pesticides used on crops can harm human, animals, and beneficial insects.
WHY DESIGNER PLANTS?
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Use of genetically modified crops may allow use to reduce our dependence upon
and use of harmful pesticides and fertilizers.
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They may also allow us to reduce the amount of land we have to cultivate,
preserving some of that land for wildlife and reducing our impact on the
landscape and the environment, while still feeding our ever-growing population.
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Higher yielding GM crops can help us to produce enough food to feed all of the
people of the world.
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In addition, genetically modified crops may help people that rely on agriculture for
food and income in drought-stricken, impoverished regions of the world.
DESIGNER PLANTS
DESIGNER PLANTS: THE CONTROVERSY
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The most commonly planted GMO crops include corn, sorghum, cotton, soy,
canola, and alfalfa that genetically modified to be resistant to the herbicide
glyphosate.
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Instead of having to till the soil to get rid of weeds, farmers can spray their crops
with this herbicide, which will kill weeds but not the crops.
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However, weeds are developing resistance to this herbicide so that spraying it
does no good.
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In addition, the engineered gene is also appearing in wild plants and nonengineered crops, indicating that transgenes can do escape in to the environment
as a result of being transferred from GM plants to non-GM plants by pollen carried
by the wind or by insects.
BIOTECH BARNYARDS
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The first genetically modified animals were mice.
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Today these mice are very common and are invaluable in research.
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As discussed earlier in this chapter, we have discovered the function of many
human genes by “knocking-out” their counter-parts in mice.
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Also, genetically modified mice serve as a model for use to study many human
diseases such as diabetes.
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Researchers can knock-out the genes that control glucose metabolism in a strain
of mice and study the effects of these knockouts.
BIOTECH BARNYARDS
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Researchers have also created genetically modified animals that make proteins that have
medical and industrial significance.
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For example, transgenic goats have been created that produce proteins that are used to treat
cystic fibrosis, heart attacks, and blood clotting disorders.
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Transgenic goats have also been created that produce humanized milk.
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Specifically, these goats’ milk contains lysozyme, an antibacterial human protein that can
prevent infants and children in developing countries from suffering from diarrheal diseases.
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In addition, researchers are engineering goats to produce milk containing spider silk (for
producing fabrics), rabbits that produce a human protein (interleukin-2) to treat immune
disorders, goats that produce heart healthy milk, pigs that are low fat, sheep that are extra
large, and the list goes on and on.
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**Explain your own example of a genetically modified animal that has not been discussed in
this presentation or your textbook. What was the purpose/benefit of creating this animal?
BIOTECH BARNYARDS
KNOCKOUT CELLS AND ORGAN FACTORIES
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Animals could be the new source of organs for transplantation into humans.
Millions of people suffer with organs and tissues that are damaged beyond repair.
80,000 people are on the waiting for an organ transplant at any one time.
Because human organs are in such high demand and such short supply, human organ
trafficking has become a common problem.
Since pig organs are about the same size as human organs, pigs could serve as a source
of organs for humans if we could rid the pig organs of their cell surface proteins that
identify them as foreign to the human immune system.
Researchers have produced genetically modified pigs that lack these cell surface proteins
in order to prevent human immune system rejection upon transplantation.
Transplantation of pig organs into humans is called xenotransplantation.
The major concern about this practice is that it could lead to pig viruses crossing the
species barrier and infecting humans.
This is of major concern since evidence suggests that some of the worst viral outbreaks
have occurred when animal viruses cross over into humans (for example, AIDS).
GENETICALLY MODIFIED HUMANS:
GETTING BETTER
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We are aware of over 15,000 genetic disorders.
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Collectively, they are responsible for 20 to 30 percent of infant deaths every year,
half of all mentally impaired patients, and one fourth of all hospital admissions.
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They also cause age-related disorders including cancer, Parkinson’s disease and
diabetes.
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Although drugs and other treatments can minimize the symptoms of these
disorders, gene therapy is the only cure.
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Gene therapy is the transfer of recombinant DNA into an individual’s body cells,
with the intent to correct a genetic defect or treat a disease.
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The transfer of the recombinant DNA is done by viruses or by lipid clusters.
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These vectors are able to insert an unmutated gene into an individual’s DNA to do
the job not being done by a mutated gene.
GENETICALLY MODIFIED HUMANS:
GETTING BETTER
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Gene therapy is now being used to treat genetic disorders such as cystic fibrosis,
hemophilia A, certain types of cancer, as well as diseases of the eye, the ear, and
the immune system.
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In a specific example, a gene therapy for cystic fibrosis has been developed in
which researchers genetically modify a flu virus by removing the gene that causes
it to be pathogenic and inserting an unmutated gene into the virus.
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The CF patient then breathes in the genetically modified flu virus.
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The virus infects the lungs cells, inserting the unmutated gene into the DNA of the
patient’s lung cells, causing the functional protein to be produced that allows the
proper transport of chloride ions and water across the lung epithelial tissues.
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However, this gene therapy is only a temporary solution, since the body’s immune
system recognizes the viral DNA as foreign and destroys it, causing this therapy to
last only about 6 months after treatment.
GENETICALLY MODIFIED HUMANS:
GETTING BETTER
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In a more permanent example, a gene therapy has been developed for the severe
immune disorder, SCID-X1.
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SCID-X1 is a genetic disorder caused by a mutation in the IL2RG gene, which codes for
a receptor for an immune signaling molecule.
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Children who are affected by the genetic disorder are able to survive only in germ-free
isolation tents because they cannot fight infections.
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In 1998, a virus was used to insert unmutated copies of the IL2RG gene into bone
marrow cells from 11 boys affected by SCID-X1. Bone marrow cells were used because
bone marrow is responsible for producing blood cells, including white blood cells, which
make up a major part of the body’s immune system.
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The genetically modified cells were then inserted back into the children.
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Within a few months, 10 of the 11 boys were able to leave their isolation tents
permanently because the genetically modified virus used for this gene therapy was
able to repair the boys’ immune systems.
GENETICALLY MODIFIED HUMANS:
GETTING BETTER
GENETICALLT MODIFIED HUMANS:
GETTING BETTER
GENETICALLY MODIFIED HUMANS:
GETTING WORSE
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Manipulating a gene within a living human is very unpredictable even when we know the gene’s
sequence and where it is located within the genome.
The very gene therapy that was used to make an individual better can actually take his or her life
when unpredictable side effects occur.
For example, in the SCID-X1 gene therapy trial, 3 of the 11 boys developed a type of bone marrow
cancer called leukemia and one of them died.
Cancer as a result of gene therapy occurs because the the virus inserted its DNA into a location in
the patient’s DNA that caused an interruption of genes that are responsible for the control of cell
division.
In another example, an 18 year old boy had a rare deficiency of a liver enzyme caused by a genetic
mutation.
This liver enzyme helps to break down ammonia, which is a by-product of the break down of proteins
in the body.
The young man’s health had been fairly stable as long as he remained on a low-protein diet.
In 1999, he volunteered to participate in a gene therapy trial for his disorder.
He suffered an allergic reaction to the viral vector used in the trial and four days later, his vital
organs shut down and he died.
GENETICALLY MODIFIED HUMANS:
GETTING PERFECT
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The idea of selecting the most desirable trait is called eugenics.
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This idea, though harmless sounding enough, has been used as a justification for
some of the most horrific events in history, including the genocide of 6 million
Jews during World War II.
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Most people would agree that it’s ok to use gene therapy to improve the lives of
or even cure individuals suffering from genetic disorders.
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But where do we stop?
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Is it ok use genetic modification to have a child with enhanced learning ability,
improved memory, bigger muscles, or longer lives?
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Mice have already been genetically engineered to have traits such as these. Why
not humans?
GENETICALLY MODIFIED HUMANS:
GETTING PERFECT
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Creating gene therapies and cures might not be very profitable for companies involved
in this research, but getting paid to ensure that parents have their “perfect” child
might.
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Would you be willing to pay to ensure that your child would be tall or blue-eyed, have
super human strength or intelligence?
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How many people do you know who would be willing to pay for a treatment that might
help them permanently lose weight?
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Would you be willing to pay for a cuter smarter baby? A less aggressive child or one
who would definitely grow up to be heterosexual?
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MANY parents would.
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Where do we draw the line or can we?
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The question today is not how would we do this because we already know how. The
only question today is how do we choose the traits that are ok to manipulate?
GENETICALLY MODIFIED HUMANS:
GETTING THERE
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Some people insist that we should never genetically modify anything.
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They feel that, when it comes to genetic modification, we are on a “slippery slope”
that may not only irreversibly damage us but also our entire biosphere.
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Has our ability to tinker with genetics surpassed our ability to understand the
impact of our tinkering?
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What are we missing out on if we don’t take these risks?
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Do we have the right to impose the consequences of taking these risks on those
people who choose not to take them?
DRAWING LINES
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**Consider all of the types of genetic modification we have discussed and ways
that we can perform these techniques. If you could draw a line to restrict genetic
modification, where would you draw it and why? Would you draw the line at all?
Explain.