《2025年凤凰新学案高中英语必修第一册译林版》

B
Some people often wonder whether they are fighting a battle with their genes to maintain a healthy weight. In fact, researchers have provided plenty of evidence that people are born with tendencies to be lighter or heavier. For example, studies of identical twins（同卵双生）have revealed great similarity in their overall weight. Part of this similarity may be explained by the finding that some people are born to burn a lot of calories just through ordinary day-to-day activities while others are not. Those who are not are more at risk from weight gain.
Researchers have discovered some of the actual genetic mechanisms（机制）that may make some individuals more likely to be
obese. For example, a gene has been found that appears to control signals to the brain that enough fat has been stored in the body in the course of a meal—so the individual should stop eating. The gene influences the production of leptin（瘦蛋白）, which keeps appetite under control. If leptin doesn’t work well, it is likely that individuals will continue to eat. Thus the gene that controls leptin appears to have a critical influence on the potential for obesity.
The confirmation that leptin plays a role in weight control has encouraged researchers to identify and understand other weight-related genes. Recent attention has focused on a gene called GAD2. GAD2 helps control the amount of the neuro-transmitter（神经递质）GABA. In general, when more GABA is available, appetite is increased. For that reason, people who have a form of GAD2 that allows more GABA to be available may be at risk from overeating. You can see that GAD2 is not directly an obesity gene. Rather it has an indirect influence on obesity through its direct influence on GABA.
Genetic research holds out the promise of innovative solutions to obesity. Researchers hope that an understanding of the link between genes and weight control will enable them to provide new drug treatments. Nonetheless, even the most optimistic researchers provide a warning: “Innovative drugs will be effective only when they are used along with lifestyle changes.”
5. What does the writer want to explain by giving the example of twins?
A. It is hard to maintain a healthy weight.
B. Being fat or thin is genetically related.
C. The twins are usually of similar weight.
D. An individual’s body can burn calories.
6. What can make an individual more likely to put on weight?
A. Poor appetite.
B. All varieties of GAD2.
C. Effective leptin.
D. Extra amount of GABA.
7. What do researchers suggest people do?
A. Adopt advanced means.
B. Learn more about genetic effects.
C. Keep good living habits.
D. Change the weight-related genes.
8. What is the passage mainly about?
A. How does genetics contribute to obesity.
B. What impact does eating have on weight.
C. How many genes determine who is obese.
D. Why do many people become overweight.

答案： 5. B 写作手法题。根据第一段第二句以及第二段第一句可知，作者想通过双胞胎的例子来解释胖或瘦与基因有关。故选 B项。
6. D 细节理解题。根据第三段可知，额外的 GABA 可能会使人食欲过于旺盛，进而容易发胖。故选 D项。
7. C 细节理解题。根据最后一段最后一句可知，研究人员建议人们保持良好的生活习惯。故选 C项。
8. A 主旨大意题。通读全文可知，本文主要介绍的是研究人员发现体重和基因存在关联，一些遗传机制可能使某些人更容易肥胖。故选 A项。