雅思阅读 100: When Doping Becomes Genetic（当作弊改写了基因）

改编自 PMC / WADA Technical Documents（2021–2025年）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://pmc.ncbi.nlm.nih.gov/articles/PMC4203840/

Reading Passage

A. For half a century, the fight against doping in sport was fought with chemistry. Athletes swallowed or injected foreign substances — steroids, stimulants, hormones — and laboratories searched urine and blood for molecules that nature did not put there. Gene therapy, originally devised to treat genetic disease, promised to upend that familiar contest. Instead of adding a substance from outside, it offered the chance to alter the athlete's own cells so that the body itself manufactured the advantage. Because the product is chemically indistinguishable from the body's own, and because the "drug" sits inside the genome rather than floating in the bloodstream, the old laboratory tests were suddenly staring at a problem they had not been built to solve. Anti-doping scientists call the practice gene doping, and they have spent two decades preparing for a threat that may already have arrived. The same technology that cures a child's inherited blindness can, in the wrong hands, hand an athlete a permanent advantage — and the line between therapy and enhancement turns out to be disturbingly easy to cross.

B. The textbook example is the gene for erythropoietin, or EPO. This hormone, normally made in the kidneys, tells bone marrow to produce red blood cells; more red cells mean more oxygen carried to working muscle, which is exactly what an endurance runner or a cyclist craves. The conventional version of the cheat was to inject lab-made EPO; gene doping goes a step further. A harmless virus is engineered to carry an extra, artificial copy of the EPO gene into the athlete's muscle or liver, where it settles in and instructs the cells to pump out the hormone indefinitely. A single procedure could, in principle, supply the boost that formerly required repeated injections. A parallel approach targets myostatin, a protein that normally restrains muscle growth; switch it off, and muscle mass climbs without a single lift, turning a lean athlete into an unusually powerful one almost overnight. In both cases the body no longer uses a drug; it becomes the drug, churning out the altered protein from its own cells. The advantage, once inserted, is not flushed out with a urine sample but persists for months or years, which is exactly what makes it so tempting — and so dangerous.

C. The reason the practice is banned — rather than merely tolerated as the next frontier of training — is that it is extraordinarily dangerous. Turning up EPO without a thermostat thickens the blood. The proportion of red cells, the haematocrit, can climb past the point at which the blood flows like syrup through the smallest vessels, raising the risk of clots, stroke and heart attack in a sleeping body. Early experiments on animals showed exactly this: overexpressing the gene produced such densely packed blood that survival itself was uncertain. Viral vectors also carry their own risks, provoking immune reactions that have killed people in legitimate therapy trials. The same alteration that wins a race can, without fine control, end a life — and an athlete desperate enough to undergo the procedure is, by definition, unlikely to be a careful judge of the risks. A procedure that goes wrong in the lab may kill the very competitor it was meant to crown. The history of EPO doping already records athletes who pushed their own blood too far; gene transfer simply removes the syringe and leaves the thermostat permanently wide open.

D. Detecting the manipulation has therefore become one of anti-doping's hardest puzzles, and the clever solution exploits a quirk of genetics. A natural human gene is not a continuous stretch of code; it is broken into useful coding segments separated by non-coding stretches called introns, which are spliced out when the cell makes the final working copy. A transferred therapeutic gene, by contrast, is usually built as a compact "complementary DNA" — intronless by design. Laboratories can now use the polymerase chain reaction to hunt precisely for this tell-tale, intron-free sequence in a blood sample: if it appears, the extra copy was inserted artificially. The elegance of the method is that it looks for the act of editing itself, not for the performance-enhancing result of it. Modern screening can also be done on a dried blood spot, a tiny drop of blood dried on paper that is far easier to collect and store than a full sample, which allows testers to sample athletes almost anywhere, on any day, rather than relying on a controlled doping-control hour. The aim is not merely to catch the cheat but to make the risk of being caught high enough that the procedure becomes, for a rational athlete, a bad bet worth refusing.

E. The detectives acknowledge that their tools are imperfect. A natural genetic variant in the EPO gene can, by coincidence, produce a protein that looks like the recombinant product, threatening a false accusation against an entirely clean athlete; analysts must therefore distinguish the two carefully. The deeper worry is a familiar one: detection technology always chases the latest trick, and a determined cheatsheet will keep trying methods that the laboratories have not yet learned to see. Yet the very fact that the chase has moved to the genome shows how far detection has come: where once the question was whether a drug was present, now it is whether the code itself has been altered. What the gene-doping era has made undeniable is that sport's problem is no longer merely chemistry. It has become a question of reading the code of the body itself — and of proving, from a single drop of blood, whether a champion's edge was earned in training or written into their cells. The laboratory that catches a gene, in the end, protects not the rulebook so much as the ideal that every runner began the race on equal terms.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. From injecting hormones to editing the athlete's own cells ii. How an extra EPO gene would actually work iii. Why the shortcut can be lethal iv. Hunting the tell-tale intron-free sequence v. The detectives admit their tools are imperfect vi. The history of the Olympic Games vii. Why blood tests have been abolished

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why is gene doping harder to catch than traditional doping? A. The advantage is produced inside the body's own cells. B. It affects only athletes under the age of eighteen. C. It leaves no chemical trace in urine or blood. D. It is impossible for viruses to carry genes.

6. What would an extra EPO gene aim to achieve? A. To reduce the athlete's blood volume. B. To increase red blood cells and oxygen carried to muscles. C. To build muscle without exercise. D. To slow the heart rate permanently.

7. Why is raising EPO uncontrolled so dangerous? A. It turns the blood too watery. B. It raises haematocrit, thickening the blood and risking clots. C. It causes temporary deafness. D. It lowers the heart rate to a fatal level.

8. What genetic feature lets laboratories spot an inserted EPO gene? A. The transferred copy lacks the introns present in natural genes. B. It changes the colour of the athlete's urine. C. It makes all genes disappear. D. It can only be detected by MRI scanning the brain.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. A conventional EPO injection and an EPO gene transfer produce the same hormone.
10. Switching off myostatin tends to reduce an athlete's muscle mass.
11. Viral vectors used in gene therapy have never caused serious immune reactions.
12. A dried blood spot can be easier to collect and store than a full blood sample.
13. No athlete has ever tested positive for gene doping in the Olympics.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Natural genes contain non-coding stretches called (14) __________, which are absent from the compact artificial copy; laboratories use the polymerase (15) __________ reaction to hunt for this difference.

答案与解析

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