[紧急求助]天山-3-27

  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.

Q27:

The primary purpose of the passage is to

A.  summarize findings in an area of research

B.   discuss different perspectives on a scientific question

C.   outline the major questions in a scientific discipline

D.  illustrate the usefulness of investigating a research topic

E.   reconcile differences between two definitions of a term

明天就考试，这题看了所有的讨论还是不能确定。。。我觉得C更合理，，，，但指的是一个学科，还是所有的学科。。。

discussion from before:

中心句  Researchers studying how genes control animal behavior have had

我个人选B，因为我觉得文章的第一句是为了引出后面的讨论，而对讨论提出的一个背景，C中的in a scientic displine,应该是不对的，文章中用researchers in different fields 强调了不同的displine.

个人看法，谨供参考。祝考试顺利！