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
files 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?
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
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.

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