A
A freshly baked roll is as delightful as a soft, light cloud on a summer’s day. What gives bread much of its appealing texture is gluten(麸质), a group of proteins found in wheat. But in people with celiac disease(乳糜泻), gluten damages the small intestine(肠). Many others may have milder gluten intolerance and avoid foods that contain it.
Most gluten-free bread is made from alternative flours such as rice or potato, so it tastes and feels different from wheat bread. Now, however, researchers say that they have found a way to genetically engineer wheat that contains far less of the most troublesome type of gluten — but still has other proteins that give bread its characteristic taste and springiness.
Genetically modified crops are the subject of fierce debate around the world. The biggest concern involves the practice of inserting DNA from one species into another, says Francisco Barro, a plant biotechnologist. To avoid this genetic crossover, Barro and his colleagues used the gene-editing technique CRISPR／Cas9 to cut selected genes from a wheat genome(基因组).
Their study zeroed in on alpha-gliadins(α-胶质蛋白), gluten proteins believed to be wheat’s major troublemakers in the immune system. The researchers designed bits of genetic material that directed the scissor-like Cas9 protein to cut out 35 of the 45 alpha-gliadin genes.When the modified wheat was tested in a Petri dish, it produced an 85 percent weaker immune response, the team reported online last September in Plant Biotechnology Journal.
Wendy Harwood, a crop geneticist at the John Innes Center in England, who was not part of the study, notes that the engineered wheat has a long way to go before it can be turned into anything marketable. “I don’t think it’s the end of the story.” she says. “This is just a really important step in maybe producing something that is going to be incredibly useful.” To develop a completely safe strain of wheat for celiac patients，the researchers may need to target more of the gluten genes. Barro says his team is working on that.
21. What’s the text mainly about?
A. Making gluten-free bread.
B. Advantages of gluten-free wheat.
C. Debate about genetically modified crops.
D. Developing genetically engineered wheat.
22. Why is bread mentioned in paragraph 1?
A. To advertise a new study.
B. To raise the topic to be written about.
C. To provide some advice for the readers.
D. To popularize some information about medicine.
23. What concerns people most according to paragraph 3?
A. Genetic crossover. B. Gene-editing technique.
C. The practice of using DNA. D. The subject of fierce debate.
24. What’s Wendy Harwood’s attitude towards engineered wheat?
A. A little alarmed. B. Mildly surprised.
C. Somewhat opposed. D. Cautiously optimistic.
