Download will dna technology let parents design their kids?

Genetically perfect ValJds await
their instructions in a scene from
Gattaca.
rid Wickeigren
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WILL DNA TECHNOLOGY LET PARENTS DESIGN THEIR KIDS?
In the 1997 .science-ficiion inovic Gaiiaca. lead cluiructer
Vincent Freeman is one of the "In-Valicls." When Freeman
was a baby, a test of his DNA revealed that he would grow
up to have bad eyesight and die at age 30. With such poor
prospects, he was slotted into the bottom of society and
given a dead-encljob. But Vincent dreams of becoming an
astronaut. So he borrows the genetic identity of a "Valid,"
a man with desirable DNA. Shortly before Vincent's
spaceflight is due for takeoff, a murder investigation
threatens to expose his true genetic self.
A
t the Fertility Institutes in Los Angeles, a
young married couple awaits an important
result. The husband has donated sperm to
fertilize an egg donated by his wife. The
resulting embryo (fertilized egg) has been
given a DNA test to determine whether it carries a certain mutation, or change in a gene, that causes a specific
disease. If it doesn't have the mutation, the embryo will
be transferred to the wife's womb.
In fertility clinics across the country, prospective parents now routinely have their embryos genetically tested
for life-threatening ailments. Hundreds of tests for genetic
diseases are available—more than IO() of them can be
done on embryos—and the number is growing.
One test looks for the mutation that causes hemophilia.
a disorder in which the blood is slow to coagulate (clot).
Another test looks for the mutation that results in TaySach.s. a disease that severely damages the brain. Another
lest .scans for a mutation that causes males to be infertile.
Tay-Sachs and hemophilia are caused by mutations in
a single gene. DNA tests cannot pinpoint every child's
10 CURRENT SCIENCE December 3, 2004
chances of devclopuig diseases that are influenced by
many genes, including heart disease and cancer. However,
tests for such conditions are probably not far off. Tests for
personality traits, such as intelligenee or aggressiveness,
may come too.
"There is a huge amount of interest in risk profiling—
that is, being able to say that a person has a 99 percent
chance of developing, say, heart disease by age 30," as
doctors do in Gattaca, says Harry Ostrer, a geneticist at
New York University School of Medicine.
GENETIC ID
Today, the number of genetic tests that can be performed
on any one embryo is limited. One reason is expense:
Each test costs anywhere from $100 to several thousand
dollars. Performing more than 14 genetic tests on a single
embryo is also technically difficult.
That could change soon. Scientists are working on
techn(5logy that could instantly and cheaply read and
interpret an individual's entire genetic code at once,
instead of testing for each disease separately.
Such technology could bring about a Gattaca-Vikc test
that reveals an embryo's chances of contracting any of
thousands of diseases as well as leanings toward aggression, studiousness. and other personality traits. "By 2025.
we will probably have developed low-cost genetic risk
profiles" Ostrer toid Current Science.
BIOLOGICAL BARRIER?
Where might genetic profiling lead? To a new social
order, like the world ol' Gattaca'! Might the best schools,
the best jobs, and the best health cure be reserved for
Ihe people with the best geiielie profiles?
Thai sort of genetie discrimination doesn't just
h;ippen in the movies. In the early 1970s, after a test
lor the blood disorder sickle-eell anemia was developed,
ehildien were routinely tested for the mutation that
eauses the disease. Some adults who were tested were
denied jobs based on the results of the test.
Might DNA profiling also lead to a form of eugenics—
the improvement of a population by selective breeding—
in which parents are told whieh cliildren they can hring
the world? "In Gattaca. there was a coercive aspect
about it," said Ostren "The geneticist said to the parents,
'We've selected these etnbryos for you." "
Even if parents aren"t told what to do. they might
still feel social pressure to provide their children with
the best possible set of genes. "You can imagine that if
a technology is available thai allows you to pick the best
embryo—^you could feel like an irresponsible parent if
you don't do that." said Kathy Hudson, the director of
the Genetics and Public Policy Center at Johns Hopkins
University. Children born without the use
of
such technology might be regarded as
SEX S E L E C T I O N
inferior.
But would they grow up to be
At fertility clinics, parents can choose the sex of their child if they wish to. Both
lesser human beings?
males and females normally carry 23 pairs of chromosomes, structures inside the
cells that contain a person's DNA. The difference between males and females ties in
the 23rd pair. Girls have two X chromosomes, white boys have one X chroinosome
(right) and one Y chromosome (left). To identify the sex of an embryo before
imptanting it into the mother, a fertility doctor stains the emhrgo's chromosomes
so that any X chromosome appears
one color and any Y chromosome
appears another. Bg looidng at
the colored chromosomes .,
"^
under a microscope,
the doctor can easily
tetl whether the embryo
is male or female.
.
-'1' ''.'
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,
NATURE VERSUS NURTURE
Genes are not destiny. Genes shape
many personality traits, but so does
environment.
In Gattaca, Vincent manages to
qualify for the space program despite his
"inferior" genes. His strongest trait is his
willpower—something tliat, the movie
implies, cannot be fathomed from genes
alone. "Our behaviors are way more
complex than genetics." said Hudson.
The same is even true for heart disease,
which diet and exercise may influence as
much as genes do. Vincent keeps himself
physically fit and. perhaps as a result, does
not die when predicted. "My heail." he
says, "is already lO.OtK) beats overdue." CS
December 3, 2004 CURRENT SDENCE 11