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  3. Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behavi

Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behavi

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问题 Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behaviors are governed by more than one gene, and until recently geneticists had no method for identifying the multiple genes involved. In addition, even when a single gene is found to control a behavior, researchers in different fields do not necessarily agree that it is a "behavioral gene." Neuroscientists, whose interest in genetic research is to understand the nervous system (which generates behavior), define the term broadly. But ethologists—specialists in animal behavior—are interested in evolution, so they define the term narrowly. They insist that mutations in a behavioral gene must alter a specific normal behavior and not merely make the organism ill, so that the genetically induced behavioral change will provide variation that natural selection can act upon, possibly leading to the evolution of a new species. For example, in the fruit fly, researchers have identified the gene Shaker, mutations in which cause flies to shake violently under anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In contrast, ethologists do consider the gene period (per), which controls the fruit fly’s circadian (24-hour) rhythm, a behavioral gene because flies with mutated per genes are healthy; they simply have different rhythms.
The passage suggests that neuroscientists would most likely consider Shaker to be which of the following ?
选项 A、An example of a behavioral gene
B、One of multiple genes that control a single behavior
C、A gene that, when mutated, causes an alteration in a specific normal behavior without making the organism ill
D、A gene of interest to ethologists but of no interest to neuroscientists
E、A poor source of information about the nenous system
答案A
解析 Application
The passage asserts that ethologists do not regard Shaker as a behavioral gene because it merely makes fruit flies exhibit unhealthy behavior (shaking under anesthesia). But neuroscientists, according to the passage, are mainly interested in how genes, via the nervous system, contribute to behavior. The passage suggests that neuroscientists, unlike ethologists, have no reservation about using the term behavioral gene to apply to any gene that contributes to behavior. The implication is that neuroscientists would probably regard Shaker as a behavioral gene.
A Correct. The passage suggests that neuroscientists would probably regard Shaker as a behavioral gene.
B The passage indicates that research shows Shaker is a sufficient cause, in fruit flies, of shaking under anesthesia. Although some organism might display a behavior controlled by Shaker in concert with other genes, the passage is silent on any such possibility.
C The passage lacks information as to whether there is any alteration—one that neuroscientists would likely consider healthy—in a normal behavior if the alteration is caused by a mutation in Shaker.
D The passage indicates that neuroscientists’ interest in genetics is part of their effort to understand the nervous system. This seems to imply that neuroscientists might be interested in Shaker.
E The passage is silent on how neuroscientists would evaluate the potential for Shaker to contribute to understanding of the nervous system.
The correct answer is A.
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