Modern Science - A Blessing or a Curse?

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Vorüberlegungen

Ideenbörse Englisch Sekundarstufe II, Heft 15, 06/2003

Lernziele:

• Die Schüler erweitern ihre Techniken im Umgang mit Sachtexten aus englischsprachigen Magazinen.

• Textstrukturen zu erkennen, die Intention des Autors zu betrachten und dabei sachliche Informationen aufzunehmen, steht im Umgang mit den vorliegenden Texten im Vordergrund.

• Der Wortschatz wird entsprechend dem thematischen Schwerpunkt erweitert. Fachbegriffe werden dabei explizit erläutert.

• Sprechanlässe verschiedenster Art fördern die kommunikative Kompetenz.

• Die Analyse- und Interpretationsfähigkeit der Schüler wird durch die Textarbeit ausgebaut.

• Die Schüler sollen sich kritisch mit den Vor- und Nachteilen von Genmanipulation auseinander setzen und neue Erkenntnisse und Einblicke gewinnen.

Anmerkungen zum Thema:

In einer Zeit, in der Eingriffe in natürliche Prozesse an der Tagesordnung sind, erscheint es unerlässlich, gerade die Themenbereiche, die den Alltag maßgeblich beeinflussen, immer wieder anzusprechen und bereits vorhandene Kenntnisse zu aktualisieren, damit eine kritische Sichtweise möglich wird. Aus dem Fach Biologie bringen die Schüler mit Sicherheit ein angemessenes Grundwissen in Bezug auf Begriffe wie DNA, RNA oder Genmanipulation mit. Gerade deshalb wird es interessant sein, sich einmal in einem ande- ren Fach zu diesem Thema äußern zu können, die Meinung anderer Mitschüler zu hören und darüber zu dis- kutieren.

Literatur zur Vorbereitung:

Newsweek: Special Issue, December 2001 Newsweek: February 24, 2003

Die einzelnen Unterrichtsschritte im Überblick:

1. Schritt: An Introduction to Nucleic Acids 2. Schritt: DNA on the Dinner Table

3. Schritt: Truth, Beauty and the Double Helix 4. Schritt: Identity Crisis

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Unterrichtsplanung

1. Schritt: An Introduction to Nucleic Acids

Der Text “Nucleic Acids” (vgl. Texte und Materialien M 1) soll zunächst als Infoblatt für die Lehrkraft dienen. Einige Fachbegriffe und biologische Zusammenhänge werden neben einem kurzen geschichtlichen Abriss beschrieben.

Für die Schüler sind als Einstieg in die Thematik zwei Abbildungen vorgesehen (vgl. Texte und Materialien M 2). Es handelt sich um zwei Kunstwerke, die sich mit eben dieser Thema- tik befassen. Beide wurden in Ausstellungen dargeboten, die zu Ehren des 50. Jubiläums der Entdeckung der DNA double helix stattfanden. Den Schülern soll zunächst Suzanne Ankers Werk präsentiert werden (auf Folie oder als Kopie). Die folgenden Fragen könnten dabei hilf- reich sein:

• Have a look at that. What comes to your mind?

• What is that supposed to show?

• Do you like it? Why/why not?

• Would you visit one of those exhibitions that celebrate the 50^th anniversary of the discovery of the DNA double helix?

Anschließend sollte den Schülern das zweite Kunstwerk gezeigt werden. Der Titel des Bildes kann dabei zunächst unerwähnt bleiben. Die Schüler sollen sich das Bild ansehen, sollen es be- schreiben, überlegen, was dargestellt wird und sich außerdem einen Titel ausdenken.

Einige Schüler wissen sicherlich auch faktisch einiges über DNA, Gentechnik oder Genmani- pulation. Es bietet sich daher an, den Schülern die Möglichkeit zu geben, einiges von ihrem Wissen mitzuteilen.

Falls in einem Kurs auffällt, dass sehr wenig Hintergrundinformation vorhanden ist, kann der Text “Nucleic Acids” (vgl. Texte und Materialien M 1) mit den Schülern besprochen werden.

Er kann auch in Stillarbeit oder als Hausaufgabe selbstständig bearbeitet werden.

Eine Alternative wäre sicherlich ein entsprechendes Referat zur Thematik zu hören.

2. Schritt: DNA on the Dinner Table

Der Text “DNA on the Dinner Table” (vgl. Texte und Materialien M 3; Lösungen vgl. Texte und Materialien M 4) soll in diesem Unterrichtsschritt ausführlich besprochen werden.

Zunächst wird der Text still gelesen. Im Anschluss daran werden Unklarheiten besprochen. In- nerhalb eines Unterrichtsgeprächs wird das Textverständnis überprüft.

Die Assignments können auf unterschiedliche Art und Weise bearbeitet werden. Die Fragen könnten im Unterrichtsgespräch beantwortet werden, wobei es in diesem Fall sicherlich sinn- voll wäre, einige danach als Hausaufgabe schriftlich bearbeiten zu lassen. Es bietet sich aber auch an, kleinere Gruppen oder Partner an jeweils einer Frage arbeiten zu lassen. Dabei soll- ten die Antworten im Plenum präsentiert und auch diskutiert werden.

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Unterrichtsplanung 3. Schritt: Truth, Beauty and the Double Helix

Der folgende Text “Truth, Beauty and the Double Helix” (vgl. Texte und Materialien M 5;

Lösungen vgl. Texte und Materialien M 6) greift den Gedanken “Kunst und DNA”, der im ersten Unterrichtsschritt bereits thematisiert wurde, wieder auf.

Auch hier bieten sich wieder die verschiedenen Möglichkeiten der Textarbeit an.

4. Schritt: Identity Crisis

Anschließend wird Zhang Huans Darstellung seiner Identitätskrise (vgl. Texte und Materia- lien M 7) betrachtet. Die folgenden Fragen sollen ein abschließendes Gespräch unterstützen:

• What does the artist want to express in your opinion?

• Does he consider the advantages or the disadvantages of the scientific progress concerning the DNA double helix?

• What are your personal feelings about all that?

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Texte und Materialien

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Nucleic Acids

Nucleic Acids, extremely complex molecules produced by living cells and viruses. Their name comes from their initial isolation from the nuclei of living cells. Certain nucleic acids, however, are found not in the cell nucleus but in cell cytoplasm. Nucleic acids have at least two functions: to pass on hereditary characteristics from one generation to the next, and to trigger the manufacture of specific proteins. How nucleic acids accomplish these functions is the object of some of the most intense and promising research currently under way. The nucleic acids are the fundamental substances of living things, believed by researchers to have first been formed about 3 billion years ago, when the most elementary forms of life began on earth. The origin of the so-called genetic code they carry has been accepted by researchers as being very close in time to the origin of life itself. Biochemists have succeeded in deciphering the code, that is, determining how the sequence of nucleic acids dictates the structure of proteins.

The two classes of nucleic acids are the deoxyribonucleic acids (DNA) and the ribonucleic acids (RNA). The backbones of both DNA and RNA molecules are shaped like helical strands. Their molecular weights are in the millions. To the backbones are connected a great number of smaller molecules (side groups) of four different types. The sequence of these molecules on the strand determines the code of the particular nucleic acid. This code, in turn, signals the cell how to reproduce either a duplicate of itself or the proteins it requires for survival.

All living cells contain the genetic material DNA. The cells of bacteria may have but one strand of DNA, but such a strand contains all the information needed by the cell in order to reproduce an identical offspring. The cells of mammals contain scores of DNA strands grouped together in chromosomes. In short, the structure of a DNA molecule or combination of DNA molecules determines the shape, form, and function of the offspring. Some viruses, called retroviruses, contain only RNA rather than DNA, but viruses in themselves are generally not considered true living organisms.

The pioneering research that revealed the general structure of DNA was performed by the British biophysicists Francis Crick and Maurice Wilkins and by the American biochemist James Dewey Watson. Using an X-ray diffraction picture of the DNA molecule obtained by Wilkins in 1951, Crick and Watson were able to construct a model of the DNA molecule that was completed in 1953. For their work, the three scientists received the 1962 Nobel Prize in physiology or medicine. The American biochemist Arthur Kornberg synthesized DNA from “off-the-shelf” substances, for which he was awarded, with the American biochemist Severo Ochoa (for research on RNA), the 1959 Nobel Prize in physiology or medicine. The DNA that he synthesized, although structurally similar to natural DNA, was not biologically active. In 1967, however, Kornberg and a team of researchers at Stanford University succeeded in producing biologically active DNA from relatively simple chemicals.

Certain kinds of RNA have a slightly different function from that of DNA. They take part in the actual synthesis of the proteins a cell produces. This is of particular interest to virologists because many viruses reproduce by ”forcing” the host cells to manufacture more viruses. The virus injects its own RNA into the host cell, and the host cell obeys the code of the invading RNA rather than that of its own.

Thus the cell produces proteins that are, in fact, viruses instead of the proteins required for cell function.

The host cell is destroyed, and the newly formed viruses are free to inject their RNA into other host cells.

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Texte und Materialien

White fetuses curl up among pyrite in a detail from Suzanne Anker’s “Origins and Futures”

(Foto: Newsweek)

Frank Moore: “A Train”

(Foto: Newsweek)

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Texte und Materialien

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DNA on the Dinner Table

Biotechnology: As the United States embraces genetically altered food, Europeans remain deeply skeptical. What are the risks to consumers and the environment – and what are the potential benefits?

By Geoffrey Cowley

It was just the sort of mishap that anti-biotech activists are always warning us about. In late September, tests revealed that genetically altered corn – a variety intended for livestock, not for human consumption – had found its way into millions of Kraft taco shells. The company recalled the tortillas, federal agencies reviewed the incident and the media spent weeks covering it. Yet when American consumers were asked about the scare, no one seemed worried about sprouting extra arms. The main concern was that restricting the new corn to farm animals might push up the price of a taco. “If no one´s getting sick, and no one´s dead,” one happy nosher told The New York Times, ”I´m OK with it.”

Europeans were less sanguine last spring when Aventis Crop Science disclosed that some genetically modified rapeseed had got mixed with conventional seed in shipments that reached several countries.

U.S. regulators had deemed the seeds safe for release into environment, and American fields were full of them. But on learning of the mix-up, the governments of France, Germany, Luxembourg, Sweden and the United Kingdom all ordered the resulting crops dug up and destroyed (Britain alone cleared more than 11,000 acres). Even then, citizens worried that mutant plants might have pollinated neighboring fields. The problem, according to French President Jacques Chirac´s office, is that “the majority of genetically modified products are too new for us to know exactly what the risks might eventually be.”

Biotechnology is transforming the world´s food supply, or at least America´s. U.S. growers had already planted 76 million acres of genetically modified (GM) crops as of 1999, and the number is rising fast.

Experts predict that U.S. farms will harbor more GM crops than conventional ones by the year 2020, and that virtually all nonwild plants will be genetically modified by the end of the century. But as Europeans settle into the new century, they remain deeply suspicious of the whole trend. “Food security” has become a near obsession in France, ranking second only to unemployment as a public concern. And though British Prime Minister Tony Blair has actively promoted biotech farming, British growers are loath to produce food for which there is no local market. Is such stiff resistance warranted?

Does GM farming pose real risks to health or the environment? No one denies that it could have downsides as well as advantages. But the evidence suggests that ”Frankenfood” is less dangerous than most people realize. As University of North Carolina biologist C. Neal Stewart puts it, the fears have

“escalated beyond scientific rationality.”

Farmers have spent centuries crossbreeding crops – i.e., altering their DNA – to make them produce food that is heartier or tastier or more abundant. Modern genetic science simply speeds that process.

Because they pinpoint the genes governing particular traits, bioengineers work with far greater precision than traditional plant breeders. And because genes are all made of the same stuff, useful ones can often be transferred between unrelated species. Isolate the gene that lets a soil-dwelling microbe make a natural pesticide – toxic to insects but harmless to people and other animals – and you can transfer it into food crops, enabling them to fight off bugs. Outfit a rice plant with the gene that lets dandelions produce vitamin A, and you may get a more nutritious grain. This form of agriculture is less than two decades old, but it has already spawned more than a dozen new crops. Most of today´s GM plants are indistinguishable from conventional ones, except that they are more resilient and less disruptive to the environment. But innovations now in the works could directly affect health and nutrition worldwide.

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Texte und Materialien

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Lösungsvorschläge zu Arbeitsblatt M 3

1. Which incident does Geoffrey Cowley describe in the beginning of the text and what was the American reaction to it?

Genetically altered corn had found its way into taco shells eaten by humans although the corn was invented for animals only. The American population was not really worried about that fact as long as no one got sick. They were pleased that the food got cheaper as a result of this new invention (ll. 4-10).

2. Which similar incident happened in Europe and what is interesting about the people´s reaction to it?

Rapeseed which was genetically modified was mixed up with conventional rapeseed on a ship that brought the products to Europe. The Europeans destroyed the resulting crops and even then the citizens remained worried about the neighboring fields (ll. 11-17).

3. Which reasons did Jaques Chirac give for the people’s fears?

The products are so new that we can not calculate the risks that they might cause (l. 17f).

4. What does the text reveal about farming habits in the US? Will the same be true for Europe?

By the year 2020 U.S. farms will probably harbor more GM crops than conventional ones. By the end of the century, virtually all non-wild plants will be genetically modified. The Europeans remain sceptical.

They seem to fear that GM farming poses risks to health and the environment (ll. 22-31).

5. What is meant by the term “Frankenfood”?

The author uses this term as an allusion to Mary Shelley´s “Frankenstein”. Mr Frankenstein was a scientist who created a human being out of good thoughts. He intended to create the perfect human being. The creature turned out to be evil and destructive in the end and destroyed Frankenstein´s and his family´s lives completely.

6. What does the text reveal about farming techniques?

Farmers have long tried to crossbreed and alter the crop´s DNA in order to improve the quality of their products and likewise of the food. Scientists actually have the same intention. The difference is, they work more precisely (ll. 32-40).

7. Which definitely positive effects of biotechnology and modification of plants are described?

Toxic chemicals which are thrown at crops to save them from insects pose threats to soil and water quality. Scientists found a microbe (Bt) that makes proteins that kill crop-eating insects without harming plants, animals or people. Bt-enhanced seeds caused a large cut down of pesticide use. Consequently this invention has a very positive effect on the environment (ll. 44-54).

In the near future nutritionally enhanced rice will probably provide iron and vitamin A to underfed children in Africa, Asia and Latin-America (l. 65).

In the developed world, farm-raised salmon will grow in half the time a conventional fish requires (l. 68).

Researchers are also racing to grow foods that will vaccinate kids against various infectious diseases (l. 73).

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Texte und Materialien

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8. Refer to the negative effects of GM crops.

Proteins capable of triggering allergic reactions will show up in foods that do not normally contain them (l. 76f).

GM crops might not be as environmentally friendly as they seem, because insects could develop resistance to Bt´s natural pesticides. Another worry is that weeds will gain the survival advantages of GM crops (ll. 88-101).

9. Does the author of the text favor GM farming or does he seem to be rather sceptical concerning this issue?

He seems to be convinced that well-known biologists and scientists are reliable enough so that people can trust them when they say that GM food won´t harm humans (l. 30). The fact that he talks about a strong proponent of the new agriculture in the last paragraph strengthens this assumption. So consequently he seems to favor GM farming.

10. Which means does the author use to make his text interesting and convincing?

He uses quotations of scientists and popular people (Chirac). He uses rhetorical figures (pun:

Frankenfood). He talks about different nations and their people‘s attitudes. He uses examples to make his text vivid.