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Genetically Modified Food Crops
Volume 10, Issue No. 1
About This Issue...
First Questions How is our food grown?
Which food plants are wild?
What do genes do?
What plants are safe to eat?
Can eating genes infect you?
Are all bacteria bad for plants?
Can carrots make you see better?
How many hours did you spend growing yourfood yesterday? You probably just walked to thefridge. But a hundred years ago you might haveworked more hours in the fields thanin school. In the developing world,thats still the case, and food isboth scarce and expensive.
Throughout history,peoples main concern wasproducing enough food.Civilization advanced as wedeveloped agriculture. For10,000 years we bred wild plantsto produce more food with lesswork. Agriculture got a boost inthe 1950s with new chemicals thatcontrol insects, weeds, and disease.At the same time, plant breedersdeveloped more productive varieties ofwheat, corn, and rice. Together, newfarm chemicals and improved crops led tomuch higher yields (amounts produced).This increase in production was known asthe Green Revolution.
The Green Revolution happened at a time whenthe worlds population was growing so fast thatexperts predicted massive famines. But the new,more productive crops came to the rescue. India
Whoever could make two ears of corn, or two blades of grassgrow upon a spot of ground where only one grew before would
deserve better of Mankind, and do more essential service
for his country, than the whole race of politiciansput together.
-The King of Brobdingnag,Gullivers Travels by Jonathan
more than tripled the wheat grown on the sameamount of land. There have been localized faminescaused by drought, war, and political corruption, butno worldwide starvation.
As we enter the 21st century, industrialized coun-tries are struggling with side-effects of the GreenRevolution. The overuse of agricultural chemicals is
polluting our land, wildlife, and water.In addition, the worlds
2 Genetically Modified Food Crops
Creating Better Plants ....................................... 4Weed Warriors ................................................. 6Monarch Butterfly Effect .................................. 8Golden Rice .................................................... 10Potato Power .................................................. 12Profile: Florence Muringi Wambugu ................ 14Something you can try: Growing Soybeans and Researching Monarchs .......................... 15
Volume 10, Issue No. 1
Published by:The Biotechnology Institute
In Partnership with:Pennsylvania Biotechnology AssociationBiotechnology Industry Organization
Originally Developed by:The Pennsylvania Biotechnology AssociationThe PBA Education CommitteeSnavely Associates, Ltd.
Writing by:The Writing Company, Cathryn M. Delude andKenneth W. Mirvis, Ed.D.
Design by:Snavely Associates, Ltd.
Illustrations by:Patrick W. Britten
Science Advisor:C. S. Prakash, Professor, Tuskeegee Universitywww.agbioworld.org
Special thanks to:Peggy Lemaux, Ph.D., University of California, BerkeleyWayne Parrott, Ph.D., University of Georgia
For more information:Biotechnology Institute1524 W. College Avenue, Suite 206State College, PA 16801800-796-5806www.BiotechInstitute.org
Copyright 2000, BI. All rights reserved.
The BiotechnologyInstitute is dedicated toenhancing theunderstanding of bioscience among lay audiences and infostering public education collaborations amongbioscience companies, universities, and non-profitorganizations.
Your World describes the application of biotechnology toproblems facing our world by bringing scientific discoveriesto life. We publish issues on different topics each fall andspring. If you would like information on subscribing forindividual, teacher, or library sets, or if you would like tosponsor distribution in your area, contact the BiotechnologyInstitute. Some of the fifteen back issues are available.
On the cover: For thousands of years, farmers havebeen crossbreeding plants to create better and healthiercrops. Today, scientists are using their understanding of DNAto develop plants with specialized traits, ranging from diseaseand pest resistance to better taste and nutrition.
The Biotechnology Institute would like to thank thePennsylvania Biotechnology Association, which originallydeveloped Your World.
Biotechnology & You
growing beyond the Green Revolutionscapacity to feed it. People are destroy-ing sensitive habitats to create morefarmland, but even so, there will not beenough land to feed the 9 billion peoplepredicted by 2050.
Worse, many of the worlds poor havenever benefited from the Green Revolutionbecause it did not solve the underlyingproblem: poverty. Many farmers cant affordthe chemicals and improved seeds. Millionsstill survive on a daily bowl of rice or potatoes.
They have no roads tostores, no fresh produce, and no vitamin pills and
their health suffers terribly. What can help them?Many scientists think a new Gene Revolu-
tion can help both hungry humanity andthe sensitive environment. The GeneRevolution uses biotechnology to createnew genetically modified or GM crops.
These crops can potentially produce morefood with fewer chemicals and higher
nutritional value than traditional crops.Scientists think they can improve even more
crops than the Green Revolution did: not onlygrains, but also the legumes, vegetables, roots,
and fruits that people need for a balanced,nutritious diet.
But some people worry that thesecrops are not safe to eat and couldthreaten the environment with unfore-seen problems. They questionwhether government agencies test theproducts enough and whethercorporate profit motives outweighsafety concerns. Some protestershave destroyed research laboratoriesand burned fields of GM crops.
This issue of Your World willhelp you unravel conflictingreports about agricultural biotech-nology. Is it safe and environmen-
tally friendly or an out-of-controlexperiment? You will learn how
plants with specific traits are created,how to weigh the pros and cons, andhow you can investigate these problems.
Your World 3
4 Genetically Modified Food Crops
1) Scientists copy acarrot gene thatconverts a pigment tobeta-carotene.
Plants live in a hostile world. Animals chew them, insects chomp them, pushy
plants surround them, and disease withers them. But plants are not
helpless. They make oils, smells, and poisons to fight back.
If you look at a leaf of a tomato plant under a microscope, youll see the leaf iscovered with tiny hairs. These hairs emit chemicals that act like flypaper to trap
little insects. How did this insect-fighting trait come about?
How do plants getdifferent traits?
2) They insert the carrotgene into a plasmid.
3) The plasmid isreintroduced into theAgrobacterium.
4) The Agrobacteriumtransfers the carrotgene to the cells oftomato leaves in apetri dish.
5) The tomato cells growand divide in a culturewith hormones thatencourage the cells tobecome new shootsand roots.
6) As the tiny new plantsgrow, the carrot geneconverts the tomatospigment into beta-carotene, creating anenhanced tomato.
Creating a Vitamin-Rich Tomato with a Carrot GeneThe bacterium Agrobacterium naturally infects plants. It carries some genes on a circular piece ofDNA called a plasmid and inserts those genes into plant cells. Scientists are now able to remove thebacteriums genes that cause plant disease and add a gene for a desirable trait.
Photos courtesyof Shelia Colby,University ofCalifornia, Berkeley.
Your World 5
Discoveries BehindGenetic EngineeringThe door to genetic engineering opened when scien-tists realized that all genes are written in the universallanguage of DNA. Learning to use plasmids (seeillustration) and special cut and paste proteins calledrestriction enzymes allowed them to edit DNA.Now, plant genomics is cataloging genes that couldgive plants beneficial traits, as well as genes we couldeliminate to make food safer. (See box on page 7.)
Natural SelectionWild tomatoes may have developed these tricky leaf hairs by
chance. To reproduce, plants pollinate each other. In doing so,they exchange genes the molecular instructions that producedifferent traits. The offspring have a different combination fromeither of their parents. Occasionally, genes undergo mutations(changes) during this mix. One such change made the leaf haircells produce the sticky insect-fighting proteins. This mutationgave that plant an edge over others, so it passed its insect-resistance on to new generations.
Selective BreedingAlong came the age of farming, and people noticed the insect-
resistant tomato. They selected it to pollinate other tomatoes,such as those with bigger fruits. To understand selective breed-ing, imagine that a gene is a book in a library. Different toma-toes have different versions of certain books. One plant mayhave a book for the insect-trapping flypaper. Another plant may
have a book that makes big fruits. If afarmer cross-pollinates these twoplants, eventually one offspringmight combine both traits. Butgenes dont mix individually;they come linked with otherbooks on their shelves. Thebig fruit book may come linkedto a sour fruit book. Gettingrid of that sour book might takegenerations of selective breed-
ing, if it could be done at all.Selective breeding has given us a
huge variety of plants. Over time, cultivatedvarieties have little similarity to the original wild
plant. For example, early Native Americanscultivated corn from a wild grass called
teosinte. Carrots were yellow until amutation created an orange one in the
1700s. Two thousand years ago a single gene mutation in apeach produced a nectarine. Observant farmers selected thesepleasing surprises and bred them.
Hybridizing PlantsSelective breeding has limitations. You can only breed
tomatoes with closely related plants. What if you want atomato with a trait found in a distant relative? Wild tomatoes,which are like little berries, can fight off a soil bug that attacksthe roots, but many wild varieties cant pollinate moderntomatoes. Scientists broke the pollination barrier by combin-ing their germ cells and nurturing them in a laboratory tissueculture. They produced a hybrid (mixed) tomato with theability to repel soil bugs.
Inducing MutationsCross-pollinating and
hybridizing depend on naturalvariations, and plant breederssearch the world for useful traits.To entice more variations thannature provides, scientists zap seedswith radiation and chemicals.Occasionally this method produces adesirable variety, such as a bean thatgrows as a bush rather than a vine.
Genetic EngineeringAll these methods give us some control over plant breeding,
but they are time-consuming, trial-and-error processes. Since the1980s, genetic sciences have made plant breeding more quickand precise and expanded its reach. Genomics (the study of anorganisms entire genetic instructions) is identifying genes thatproduce specific traits. Before, scientists didnt know whichbook gave the tomato leaf its sticky compound that traps insects.Now, they can pinpoint the exact book for the flypaper goo.They can pick that book off the shelf, copy it, and put it in otherplants. In this way, they make a genetically modified plant.Scientists can borrow books from unrelated species to get traitslike disease resistance, faster growth, better flavor or nutrition,or longer shelf life.
For example, tomatoes have a pigment that gives them theirbright red color and special flavor. Carrots produce a proteinthat could turn that pigment into beta-carotene, which ourbody turns into vitamin A. The illustration on page 4 showshow scientists used the natural genetic engineer, a bacteriumcalled Agrobacterium, to modify a plant. Another method coatsa tiny gold pellet with genes and shoots it into plant cells thatthen grow into plants.
Genes are in every cell of a plant,and we degrade them we eat them.We are only affected by theproteins the genes have alreadymade in the plants we eat.
Career Connection: Plant Breeder:Develop new plant varieties with needed traits.
t of E
Is genetic engineering alogical continuation of theway farmers have beenmodifying food forcenturies? Or is it anentirely new andperhaps risky process?
6 Genetically Modified Food Crops
Some of the first GM crops to hit the fields are
popular with farmers but controversial with some
people. These crops are engineered to withstand
herbicides that are sprayed on fields to kill weeds.
Weeds can take over a field, and keeping them out takesbackbreaking work. In Africa, most farmers are women, andthey spend half their time weeding! Many farmers sprayherbicide to kill specific weeds at different times. (Herbmean plant and cide means kill, as in homi-cide.) In Africa, some weeds are parasitesthat cant be sprayed without destroying thecrop. Where herbicides can be used, weedscan become resistant to them, so farmersneed ever-stronger and more diverse chemicalsto kill them. But many herbicides harm animalsand insects, and they last a long time in theenvironment.
Scientists developed less toxic herbicides toreduce these risks. One such chemical isglyphosate, which is marketed as Roundup.Glyphosate kills green plants by shutting down theproduction of essential amino acids. Insects andanimals get these compounds in their food, but
plants have to make them. To do so, a molecular key fitsinto a protein lock, turning on an essential amino acidmachine. Glyphosate mimics the key, slips into the lock, andjams it so the machine cant start. The plant starves to death!Animals dont have that molecular lock because we dont needthe machine, so glyphosate doesnt affect us. It also breaksdown quickly and doesnt stay in the environment.
If farmers sprayed glyphosate on their fields, it would killboth weeds and crops. Thus, scientists made crops thatwithstand this herbicide. They added a gene to produce aslightly different lock. The mimic key cant fit it, but the plantsown key can. The essential amino acid machine keepsworking, so the crops survive while the weeds die. Roundup
Ready crops also allow farmers to kill parasitic weeds. Thenew gene doesnt change the crop plant in any other way.
Before, farmers only had the option ofhoeing or plowing the fields to kill weedsbefore planting. This practice causes soilerosion and water pollution. With herbi-cide-resistant crops, farmers no longer haveto till, saving them work and money. Zerotillage also helps preserve the soil and water.
Farmers in the United States adopted GMseeds for crops that traditionally need a lot ofherbicides. In just four years since theirintroduction, more than half of the USsoybean crops grew from GM seeds. Did youknow you eat soybeans all the time? Look atthe labels on your snack foods!
What could happen if nofarmers used herb...