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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 contrast,

 

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.

 

 

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The passage suggests that neuroscientists would most likely consider Shaker to be which of the following?

 

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 nervous system

 

 

 

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It can be inferred from the passage that which of the following, if true, would be most likely to influence ethologists’ opinions about whether a particular gene in a species is a behavioral gene?

 

A. The gene is found only in that species.

B. The gene is extremely difficult to identify.

 

C. The only effect of mutations in the gene is to make the organism ill.

 

D. Neuroscientists consider the gene to be a behavioral gene.

 

E. Geneticists consider the gene to be a behavioral gene.

 

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

 

 

OA, A,C,B