How closely linked are genetics and behavior?

(April 11, 1998 00:19 a.m. EDT http://www.nando.net) -- Laboratory mice
usually are attentive parents, constantly herding their pups into nests and
crouching over the offspring to nurse them and keep them warm.

So why would the lab mice at the University of Washington start neglecting
their young?

Neurobiologist Steven Thomas and molecular biologist Richard Palmiter
inactivated a gene in the mice that plays a key role in preparing the brain
for motherhood.

The gene creates a protein needed to manufacture the brain chemical
norepinephrine, which is believed to promote nurturing.

When the mice with the altered gene gave birth, they left the pups scattered
around the cage, not even bothering to remove placental material. Nearly three
out of four of the pups died of neglect.

But when the surviving pups were given to foster mothers with the normal gene,
85 percent survived.

The researchers' work is part of a fast-growing field that is attempting to
answer the age-old nature-nurture question: Does biology or the environment
play a greater role in determining behavior?

More than 130 years after Austrian monk Gregor Mendel formulated the laws of
heredity while studying pea plants, researchers continue to disagree over how
much genes control destiny and what that means for public policy.

Research in behavioral genetics is different, but no less controversial, than
the burst of cloning research that has dominated news in recent months.

Though both come under the rubric of "barnyard biotech," the developmental
research does not involve the creation of new organisms.

Instead, it explores how genes in DNA carry chemical messages that may
influence behavioral traits.

Scientists since the mid-1930s have known that certain mutant genes, acting
alone or in combination with one another, can cause hereditary diseases.

Technology has since been perfected to identify the precise genetic code for
conditions such as cystic fibrosis, Huntington's chorea and Tay-Sachs disease,
and, in limited cases, physicians are applying gene therapy to treat symptoms.

But over the last two decades researchers have found ways to isolate and
characterize DNA sequences from individuals.

With these new tools, some scientists now are searching for biological
explanations to far more complex phenomena, such as sexuality, risk-taking and
violence.

Popular attention to the field was sparked by the publication of the
controversial 1994 book "The Bell Curve," in which authors Richard Herrnstein
and Charles Murray asserted that IQ is largely hereditary, and that poverty is
a function of inherited low intelligence.

Biologists, psychologists and others drawn to the field say they are concerned
about drawing similar broad societal conclusions from limited studies that
could have weaknesses in methodology.

But their work is nonetheless presenting headline-grabbing evidence that genes
may account for previously unexplainable, but commonplace, behaviors.

In 1996, a research team reported discovering a link between anxiety-related
behavior and a gene that controls the brain's ability to use a neurochemical
called serotonin -- the same neurotransmitter targeted by Prozac and other
antidepressants.

Researchers at the National Institutes of Health (NIH) and the University of
Wurtzburg in Germany found that individuals who have a slightly shorter
version of the gene for the serotonin transporter tend to be more anxious and
harbor more negative thoughts and feelings.

That same year, two groups working independently at NIH and in Israel reported
a link between excitability, thrill-seeking and quick temper and a gene
involved in the activity of the neurotransmitter dopamine, which, among other
things, transmits sensations of pleasure.

The studies focused on a segment of the gene's molecular code that is repeated
either four or seven times in a row. Novelty-seeking seemed more common in
people with the sevenfold repetition.

Since then, there have been near monthly announcements of newly discovered
suspect genes, often with the caveat that they act in tandem with other genes
and the environment to express a trait.

Arguably the most controversial connection between genes and behavior concerns
suspected links to crime and violence.

Researchers studying a dysfunctional Dutch family announced in 1993 that
aggressive behavior may be linked to a single faulty gene that causes a
shortage of enzymes needed to break down serotonin.

Since then, scientists and policy-makers have engaged in a stormy debate over
the roots of crime and possible solutions.

Proponents of continued research say that while the concept of a single
"criminal gene" may be the stuff of science fiction, biological markers exist
that could make a person more likely to commit crimes or provide clues about
populations that are more at risk.

Gene therapy to correct any inborn problems could also make an attractive and
humane alternative to incarceration, they argue.

But critics say labeling a group as predisposed to violence recalls the
eugenics movement of the early 20th century, which led to the sterilization of
convicts and some mental patients in the hope of reducing crime among future
generations.

Many social scientists say researchers, in a rush to "biologize" behavior, are
ignoring environmental influences, such as poverty, broken families and
racism.

"We tend to seek quick and easy technological conclusions that aren't always
for the public good," says Dorothy Nelkin, a New York University sociologist.

"Clearly, there are some genetic factors that contribute to behavior. (But)
it's easier to blame the individual than take up what's wrong with the social
system."

Many researchers in the pro-gene camp are uncomfortable with such criticisms
and take pains to note they are only seeking to study specific biological
systems, not prescribing broad solutions.

"When you study how a biological pathway works, you know the details, but
you're not always able to see the forest from the trees," says Judith
Greenberg, director of the division of genetics and development biology at the
National Institute of General Medical Sciences.

University of Colorado psychologist Gregory Carey says talk about genetic
advances is oversimplified and contributes to a misunderstanding of DNA's
power, especially when it comes to predicting individual traits.

"We may be able to say a certain percentage of the population is predisposed
to a condition, but I doubt we'll ever be able to identify whether Joe Smith
will have it or not," Carey says. "Any big headlines have to be taken with a
lot of caution."


By ADRIEL BETTLEHEIM, Congressional Quarterly
Copyright 1998 Nando.net
Copyright 1998 Scripps Howard

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