Genes and Even More Things 1          original text from New Scientist June 10, 2006

1)  FOR a handful of people, it has made all the difference. Around 20 boys, for instance, are now leading nomral lives. They no lon - Around 20 boys, for instance, are now leading normal lives - ger have to live sealed in a bubble because their immune systems cannot fight off diseases. And it's all down to gene therapy.

2)   Confused? Imagine if you had to rectify every spelling mistake in an article by adding a copy of the full corrected sentence at a random point. Well, that's pretty much how gene therapy and genetic engineering work right now. Instead of editing individual letters of the DNA code, you have to add a whole new piece of DNA, and there's no way to control where it ends up.

3)   Just as a stray sentence can cause confusion in a magazine article, so a stray chunk of DNA in a cell's genome can create havoc if it lands in the wrong place. In the worst-case scenario the result is cancer, as may have happened to three of 11 boys in a gene therapy trial that started in 1999 at the Necker Hospital for Sick Children in Paris, France.

4)   What is needed, say genetic engineers, is a method for altering DNA in much the same way that a word processor can correct a mistake such as "nomral". Then they could fix mutations while leaving the rest of the genome untouched, replace one version of a gene with another or insert new sequences at a precise spot.

5)   Researchers have been dreaming of this for 30 years, and now the necessary tools are starting to appear. "We are moving into a new era, into the second generation of transgenics," says Paul Eggleston of Keele University in the UK.

6)   The consequences will be profound. For starters, it will become easier and cheaper to create genetically modified plants and animals. In medicine, the precision approach promises to deliver everything from powerful new gene therapies to new treatments for diseases such as HIV. More controversially, this is the technology that could open the door to genetically engineered human beings.

7)   It is just 30 years since researchers discovered how to "cut and paste" short pieces of DNA from one strand to another in a test tube. Methods have advanced in leaps and bounds since then. In 2002, biologists in the US assembled the 7500-base-pair polio virus genome from scratch, and there are plans to do the same for a bacterial genome, hundreds of thousands of base pairs long.

8)   Altering the DNA inside cells, however, is harder. For starters, the enzymes used to splice DNA in a test tube are far too large to enter cells. Despite this, biologists now have tricks that allow them to make pretty much any change they please to bacteria such as E. coli. The more complex cells of animals and plants are a different matter. Here, DNA is packaged up with proteins and tucked away behind the double membrane of the cell nucleus. There is also a massive amount of it: 6 billion letters in 46 separate pieces (the chromosomes) in the case of humans. All this means that making precise changes is a huge challenge.

9)   As a result, most genetic engineering still relies on the discovery made in the 1970s that if you can just get a piece of DNA into plant or animal cells, it will occasionally be incorporated into the genome. Since then engineers have developed dozens of ways to deliver DNA to cells, from bombarding them with DNA-coated projectiles to hijacking the DNA delivery systems of viruses. Yet in almost all cases the final, crucial step - incorporating the DNA into the cell's genome - is down to chance. There is no way to control where the new DNA will end up.

10)   Unsurprisingly, this approach creates endless problems. For starters, random integration is a very rare event - one cell in a few thousand, if you're lucky. Integration itself brings all kinds of difficulties. Sometimes the extra DNA integrates right in the middle of another gene, rendering it useless. In the worst case this can cause cancer.

11)   Even if the DNA lands in a safe location, there is no guarantee it will behave in the way you want it to. Genomes contain numerous "switches", or regulatory elements, that control the activity of nearby genes, turning them on or off at specific times or only in specific tissues. The result is that the same piece of DNA can behave in 10 different ways in 10 different locations, depending on which regulatory elements it ends up next to. "The same gene can have very different activity," says Eggleston. That's bad news, whether you are trying create GM crops or cure genetic diseases. Indeed, some researchers think the three boys in the French gene therapy trial got cancer not because the added gene landed in the wrong place, but because it was too active.

12)   For all these reasons, genetic engineers have long sought ways to control precisely where DNA integrates into an organism's genome. Perfecting "gene targeting" would make gene therapy far safer and genetic engineering vastly more powerful.

Task 1 Vocabulary: Match the words on the right with their definitions on the left.

Word	Definition	no.
1 gene therapy	A) the study of organisms that have been altered by the transfer of a gene from another organism
2 genetic engineering	B) a thick mass or piece
3 stray	C) join with something else
4 chunk	D) the part of a cell controlling its metabolism, growth, and reproduction
5 mutation	E) lost, not in the right place
6 geneome	F) test
7 transgenics	G) a thin, pliable layer of tissue like a skin
8 profound	H) hit again and again
9 strand	I) a complete haploid set of chromosomes with its associated genes
10 enzyme	J) something that is plaited or twisted like a a rope
11 membrane	K) complex proteins that function as catalysts in biochemical reactions
12 nucleus	L) deeply important
13 bombarding	M) without specific pattern
14 random	N) treatment of medical disorders by introducing a gene into the patient’s cells
15 integrates	O) a change of the DNA sequence within a cell
16 trial	P) scientific alteration of the structure of a gene in a living organism

Task 2 Pronoun referents: answer the questions below.

Pronoun	Referent
i) What does it in paragraph 2 refer to?
ii) What does it in paragraph 3 refer to?
iii) What does they in paragraph 4 refer to?
iv) Who does we in paragraph 5 refer to?
v) What does this in paragraph 6 refer to?
vi) What does this in paragraph 8 refer to?
vii) What does it in paragraph 9 refer to?

Task 3 Structure: answer the questions below.

Question	Answer
i) What is paragraph 4 about?
ii) What is the topic sentence of paragraph 6?
iii) What is paragraph 7 about?
iv) What is the topic sentence of paragraph 8?
v) What is the topic sentence of paragraph 11?

Task 4 Comprehension: answer the questions below.

Q 1	What is the problem with genetic engineering at the moment?
A
Q 2	Who is Paul Eggleston?
A
Q 3	Two differences between bacterial cells and animal or plant cells are mentioned. What are they?
A
Q 4	Two methods of getting DNA into cells are mentioned. What are they?
A
Q 5	Two problems associated with random integration are mentioned. What are they?
A
Q 6	Even if DNA is inserted into a non-dangerous place in the cell, things can still go wrong. What?
A
Q 7	Make up a title for this passage.
A

Task 5 Question formation: look at paragraphs 8 through 11 and make up one question for each paragraph. Remember, the answer must be found in the paragraph and you must know the answer.

Paragraph	Question
8
9
10
11

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