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IS HOMOSEXUALITY in the genes?
Researchers at the National Institutes of
Health (NIH) in Bethesda, Maryland,
USA, report that a single gene transplanted into fruit flies made the males show
homosexual behaviour. This display of
homosexuality is interesting to scientists
because a gene similar to that transplanted into the fruit flies exists in
Biologists Ward Odenwald and
Shang-Ding Zhang found that the male
fruit flies with the transplanted gene
formed groups, linking together end-to-end in big circles or in long winding
rows, and rubbed their genitals with each other.
The behaviour was baffling because fruit flies are
sexually highly active creatures. If a male and a
female fruit fly are put in a
bottle, they will produce a
new generation in as little
time as 2 weeks. In fact, this
trait of the fruit flies has
made them popular with genetic researchers who are
usually interested in observations covering sevtral generations of a species.
But Odenwald and
Zhang found that the
transplanted gene does not
make the males renounce
The researchers observed
that if a male fly with the
transplanted gene is surrounded by females, he will
readily oblige by fertilising them. This
implies that the gene induces bisexual
rather than homosexual behaviour.
However, no unusual behaviour is
observed when the gene in question is
transplanted into female flies.
The DNA (deoxyribonucleic acid)
section of fruit flies that causes the
aberrant behaviour is called the "white
gene" because when it undergoes a particular type of mutation, it causes the
normal red eyes of fruit flies to turn white.
An important function of the "white
gene" is to produce a protein that
enables cells to utilise tryptophan,
which is an essential amino acid, present
in the blood. If the gene fails to perform
this function, then the red eye pigment cannot be formed.
Normally the "white gene" is present only in some cells - which include
the-brain cells - of the fruit flies' bodies. But the researchers inserted the normal version of the gene in such a way
that it got activated in every cell. This
resulted in complete mayhem in the flies' life.
As every cell sucked in tryptophan
from the blood, a paucity of the amino
acid developed in the brain. The altered
levels of tryptophan in different parts of
the insects' bodies triggered off other
A consequence was that less serotonin - a substance that transmits
impulses between nerve cells - was
made by the brain. Abnormal levels of
serotonin in humans cause extremes in
behaviour from depression to violence.
In the case of male fruit flies, the
researchers believe that a shortage of
serotonin might have led to the homosexual behaviour.
Meanwhile, gays have, by and large,
welcomed the study as it projects homo-sexuality as a trait, like skin colour,
rather than a lifestyle preference. But
some others feel that the research sees
homosexuality in the male fruit flies as
unusual behaviour, making
it seem like a "defect" that
needs to be corrected.
Says Martin Duberman,
head of the Center for
Lesbian and Gay studies,
University of New York, "If
it does turn out that for
some people, there is a
genetic or hormonal component (for homosexual
behaviour), the cry will
then arise to take care of
that." Indeed, Louis P
Sheldon, president of the
Coalition in Anaheim,
California, has already remarked that "We have to
come up with some reparative therapy to correct that genetic defect."
The evidence that genes
play a role in homosexuality in humans came to the
fore in the early '90s. A remarkable
but controversial find was that there is
a difference between the brains of gay
and straight men. And in 1993, a
researcher from NIH reported that a segment of DNA, containing I or more
genes on the X-chromosome, affects sexual orientation. But hard-core evidence linking genes to gayness is yet to be found.