Transcript Genetic Engineering

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Genetic Engineering
of Plants & Animals
Genetic Engineering: Changing the genetic
make-up of an organism using biotechnological
methods
GE: Genetically Engineered Foods
GM: Genetically Modified Foods
GMO: Genetically Modified Organisms
Transgenic Crops
Common Applications of GE
• Make crops, livestock, etc. more profitable
-- Pest resistance, herbicide resistance, shortened growth
period, traits preferred by consumer
• Make medically important substances easy to obtain
-- Enzymes, proteins, tissues
• Make transgenic animals for medical and biological
research
-- Disease models, gene function studies
Examples of GE crops
• Starlink and Bt Corn: Resistant
to common pests
• Tomatoes: “Flavr- Savr” Slow
softening ripe tomatoes
• Herbicide resistant soybeans
and cotton: “Round-up” Ready
• Tear-free onions (development
in progress)
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Cold tolerance
Cold tolerance
How do you make a GE crop?
• Identify gene that encodes trait of
interest
• Transfer DNA into plant cells via
bacteria or a gene gun.
Delivery and
Integration
• The DNA integrates into the plant’s
chromosomes
• Culture the modified plant cells to
grow many cells with the desired trait
Culture and
Differentiate
• Grow the plant cells in a special
culture that causes the cells to
differentiate
• The plantlets are transferred from the
laboratory culture to soil
http://www.agwest.sk.ca/sabic_index_tp.shtml
Bt and Starlink Corn
Bacillus thuringiensis (Bt): Soil bacterium that produces
a toxin targeting the gut of common pests of corn, such as
the European corn borer
Different forms of the
toxin (Cry proteins) can
be used to target specific
pests
Can be up to 99%
effective
Insects can develop
resistance
Starlink corn scare
Flavr-Savr Tomatoes: Antisense Technology
Isolate DNA
Polygalacturonase (PG): an enzyme
expressed during ripening causing
depolymerization of the pectin
fraction of the cell wall, which results
in softening of ripe tomatoes.
The PG gene was identified in the
tomato and inserted into a plasmid in
such a way that a PG antisense
transcript is produced
The antisense transcript binds the
PG sense mRNA blocking access of
the translational machinary
eliminating 99% of the PG product
PG
GP
Coding
Noncoding
Add CMV promoter
GP
Delivery and Integration
Antisense
suppression
of PG
GE Animals
Quick growing Salmon
Healthier Pork
Allergy-proof Cats
“Super Salmon”
A growth hormone in Salmon is normally produced only in warm
temperatures
An antifreeze protein was discovered in flounder that is expressed only
in cold temperatures
The control elements from the flounder gene were placed upstream of a
copy of the salmon growth hormone gene
The salmon with the transgene grow during the warm and cold seasons
Healthier Pork
FAD2 is found in spinach and converts saturated fats into
linoleic acid (an unsaturated fat)
The gene was placed in a pig’s genome
The transgenic pigs contain 20 percent less saturated fat
This is the first time a planet gene has been inserted into an
animal genome
Allergy Proof
Cats
Cat allergies are thought to be caused by a single protein in the
cat’s skin and saliva.
An allergen-free cat could be available by the year 2003, costing
somewhere in the region of $1000
The researchers aim to take cat cells and knock out the gene that
produces the problem protein, replacing it with an inactive version.
The cell’s nucleus will then be put into a cat egg cell, that has had
its own genes removed, creating an embryo that can be implanted
into a surrogate mother.
Making Medicine though Genetic
Engineering
Turning animals (and plants) into pharmaceutical factories
Goat’s Milk
Anti-cancer tomatoes
Pigs for organ harvest
Malaria Free Mosquitoes
Goat milk drug production
Insert gene for antithrombin III (anti-coagulate) into
goat genome with necessary signals for secretion into
milk
Purify protein from goat’s milk
Drug prevents blood clotting in patients with
antithrombin deficiency (homozygous recessive)
Cancer Preventative Tomatoes
Lycopene is a carotenoid that gives tomatoes their red
color
It is an antioxidant; carotenoids capture electrically
charged oxygen molecules that can damage tissue
People that eat lots of fruits and vegetables containing
lycopene have less breast and prostate cancers
A yeast gene is expressed in the tomato that stabilizes the
lycopene and results in 3X the amount of lycopene
Pigs for Organ Harvesting
• Xenotransplantation is limited by immune response of
recipient
• The rejection response occurs when human antibodies
attach to sugar molecules on the surface of the
transplanted pig organ's cells, killing the cells
• The gene that produces this sugar molecule, called a1,3-galactosyltransferase (GGTA1) has been eliminated
in a line of miniature swine
• The swine also have organs approximately the same
size as human organs
Malaria-Free Mosquitoes
Malaria is a deadly parasite transmitted to
humans via mosquitoes
SM1 gene: prevents malaria from entering
salivary gland from mosquito gut
SM1 was placed under control of a promoter
controlled by feeding in the mosquito
genome
Mosquitoes with SM1 were unable to
transmit malaria to mice
To effectively eliminate transmission
transgenic mosquitoes must be able to
survive as well or better than wildtype
mosquitoes
Are GE products safe?
Usually involve random insertion into genome
Includes promoters (CaMV) and enhancers
that can influence activity of nearby native
genes (may activate normally unactive genes
such as toxins)
Gene inserted is usually for a foreign protein
that could have undesirable effects in addition
to the desired effects
Many of the proteins have not previously been
eaten in food -- how will consumer be
affected?
Fusion proteins / protein folding
Environmental Issues
Cross pollination / breeding with wild species
Production of “super weeds”
Impact on other species (such as the monarch)
Have you eaten GM Food?
• The US and Canada produce 82% of the world’s GM
food.
• In 1999 almost one-quarter of our nation's food and fiber
crops were genetically engineered
• US GE Crops: 57% of U.S. soybeans, 38% of U.S. corn,
65% of U.S. cotton, 4% of U.S. potatoes, and over 50%
of the U.S. and Canadian canola crop
• 60% of processed foods sold in grocery stores contain at
least a trace of GM ingredients
What do people think about GE?
US, China, and Canada: ~75% of consumers approve
Europe and Japan: Less accepting of GM food (less than
20% approve)
But…knowledge about GE is lacking in the general public
European Survey: Would you
buy GM food?
Animals for Research
Transgenic Mice, Plants, Flies, etc.
Transgenic animals can be created to study gene
function and/or human disease genes
Can make a variety of changes to yield information
-- Null alleles (insert an antibiotic resistance gene in exon)
-- Point mutations
-- Deletion mutations (eliminate part of a gene or protein)
-- Duplications
-- Hypomorphic mutation – changes level of gene
expression
-- Controlled expression of gene in different spatial or
temporal context
Construct to Disrupt
Gene of Interest (GOI)
NEO
Transform and select
Test chimeras for germline transmittance of
brown genome
NEO
GOI
Look for chimeric
progeny
ES cell from
brown mouse
Let ES cells divide
Inject into blastocyst from
white mouse and implant
in pseudopregnant female
Links of interest...
Trangenic Pets: http://www.transgenicpets.com/
News Collections: http://www.newscientist.com/hottopics/gm/
http://www.agbiotechnet.com/topics/Database/index.asp
http://greennature.com/article299.html
Overview: http://members.tripod.com/c_rader0/gemod.htm
Labeling GM foods: http://www.thecampaign.org/
Pros and Cons: http://scope.educ.washington.edu/gmfood/
Activist Page: http://archive.greenpeace.org/~geneng/