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Researchers studying how genes control animal behavior have had
to deal with many uncertainties. In
Line the first place, most behaviors are
(5) 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
(10) 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
(15) 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
(20) 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
(25) 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
(30) anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In con- trast, ethologists do consider the gene period (per), which controls the fruit
(35) fly’s circadian (24-hour) rhythm, a
behavioral gene because files with
mutated per genes are healthy; they
simply have different rhythms.
文中出现了非常矛盾的两句话 
1。 They insist that mutations in
(20) a behavioral gene must alter a specific normal behavior and not merely make the organism ill, (即：可以使organism 不健康)
2。(30) ... Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. （这里又说：因为不健康，所以不是behavioral gene)
应如何理解呢？？
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发表于 2004-12-11 06:49:00
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