1. Read this article carefully and choose the most suitable heading from the list a – k for each paragraph in the article. The first is given as an example.

1. C

1. Disease Resistance

2. Pharmaceuticals

3. What are genetically modified foods?

4. Herbicide Tolerance

5. Cold Tolerance

6. Pest Resistance

7. Allergeniity

8. Phytoremediation

9. Some Criticism Against GM Foods

10. Unknown Effects On Human Health

11. Economic Concerns

2. Read the text carefully once again and answer these questions according to the information in the text.

1. Why do farmers use a lot of pesticides?

2. What are the three effects of treating crops with pesticides?

3. Why do farmers use weed-killers?

4. What has been done to some plants to help them tolerate cold weather conditions?

5. If a GM plant is planted, is it obviously grown as crop?

6. What types of concerns are raised about GM foods? Why?

7. Do scientists think that GM foods are dangerous to humans?

8. How can introducing GM food into the market widen the gap between the wealthy and the poor?

9. What is the possible way to avoid cross-pollinating?

10. What is bad about using the suicide gene technology?

Language Development

ǃ Past Tenses

The Simple Past is the tense most commonly used to refer to events that happened at a particular time in the past. This is very useful in science and engineering for explaining processes and procedures to show the sequence of events.

Look at this sentence from the article and underline the Past Simple Tense: Some years ago many children in the US and Europe developed life-threatening allergies to peanuts and other foods.

The Past Continuous is used to refer to activities that hadn’t been finished at the time mentioned.

Look at this sentence from the article and underline the Past Continuous Tense: A concern was growing at that time that introducing foreign genes into food plants might have an unexpected and negative impact on human health.

The Past Perfect and Past Perfect Continuous Tense are normally used to emphasize that one past event happened before another. They are very common in reported speech

Look at these sentences from the article and underline the Past Perfect Tense and Past Perfect Continuous Tenses: The scientists had created that variety of potato to test the methodology, and these potatoes were never intended for human or animal consumption.

This study claimed that there were appreciable differences in the intestines of rats fed with GM potatoes, although the scientists told that they had been feeding the rats with unmodified potatoes.

For more information refer to English Grammar in Use by R. Murphy Un.11, 12 and Un. 22, 23

1. Fill in the gaps with the proper Past Tenses. Don’t forget to put the verb into Active or Passive Voice.

Let’s review the history of genetic engineering. A scientist named Werner Arber 1. __________(study) bacterial viruses. As a graduate student at the University of Geneva in the 1950’s, he studied with a physics professor who 2. ____________(convert) from doing pure physics to biophysics. This was the 1950’s, the DNA structure and the double helix just 3. _____________ (announce), and genes were the rage in science. Even physicists 4. __________(catch) the biology bug at that period of time.

During the period of from 1960 to 1970 the scientists 5. __________(undertake) experiments with viruses and bacteria. Experiments 6.____________(include) the cloning of mice and the adding of genes to bacteria for the purposes of reproduction.

By the 1980's, scientists 7. ______________(introduce) positive proof that genes could be transferred from one plant to another and 8.____________(patent) the first genetically engineered plant. This decade 9. ______________(produce) many advances in the field.

In the early 1990s California company 10. ____________(create) a tomato, which was the first commercially grown genetically modified food crop. The tomato 11. ___________(use) to make tomato puree that 12.____________(sell) in Europe in the mid-1990s.

In 1997, a lamb born in Scotland 13.____________(become) an instant celebrity. An exact duplicate of her six-year-old mother, Dolly was the first animal cloned from the cells of an adult. Other animals previously 14. __________(clone) from the cells of embryos, but Dolly was the first animal to come from an adult. The cloning of Dolly 15. ____________(involve) several steps. First, the scientists previously 16. ______________(take) the cells from Dolly’s mother and the cells 17. ________________(starve) for five days, which 18. ____________(cause) them to stop dividing. The interruption of the cells’ division cycle 19. _____________(make) it easier for them to reprogram themselves to start growing a new organism. After five days, the nuclei of these cells 20. ________________(remove) and transferred into an unfertilized sheep egg, from which the natural nucleus previously 21. _________________(remove). In the next step, the egg was grown in the laboratory for a period of time. Then the egg was implanted into a different sheep, where it 22. ______________(grow) normally for the certain period of time. When the sheep finally 23. _____________(give) birth, the lamb was an exact genetic copy, or clone, of the sheep that 24 _______________(provide) the transferred nucleus, not the sheep that 25. ______________(provide) the egg.