Data
Yeast cells
express
green
fluorescent
protein.
GENETICS BEAT
A DIAL THAT CRANKS
UP GENE ACTION
Scientists have long used genetic switches
to turn genes on and off, but they have
struggled to control intermediate settings.
Now researchers have engineered a DNA
dimmer that allows them to adjust a gene’s
activity level. By adding measured amounts
of anhydrotetracycline (ATc) to a population of
genetically modified yeast cells, scientists
at the University of Texas M. D. Anderson
Cancer Center were able to precisely control
the production of green fluorescent protein. Doubling the concentration of ATc,
for instance, made the cells glow twice as
brightly. Even small changes in gene activity
can change cell behavior dramatically, so
this fine-tuning may open up new avenues
for studying gene function.
Just as engineers rearrange capacitors
and resistors to create different electric circuits, researchers can arrange gene promoters and repressors—stretches of DNA that
control gene activity—to create gene circuits
with different properties. Such circuits have
already been used to build a genetic clock
and to synthesize cellular machinery that
can follow basic logic commands such as
AND, OR, and NOR.
Biological physicist Gábor Balázsi says his
team’s discovery of the genetic dimmer circuit
was serendipitous. “We were originally testing for something else,” he says, “so when
we found the relationship between ATc and
fluorescence, we couldn’t believe it.” Their
next step is to investigate whether the circuit
works in mammalian cells. If so, it could help
researchers understand the effects of genes
operating at different intensities and may
eventually have applications in therapies for
genetic disorders. Jeremy Labrecque
ARCHAEOLOGY BEAT
UNEARTHING
THE MAYAN
CREATION MYTH
Archaeologists who have uncovered two massive carved stucco
panels in the Mirador Basin of Guatemala’s northern rain forest say they
are the earliest known representation
of the Mayan creation myth, predating other such artifacts by a millennium. According to the researchers,
the panels— 26 feet long and 20
feet high, with images of monsters,
gods, and swimming heroes—date
to 300 B.C. They formed the sides
of a channel that carried rainwater
into a complex system of stepped
pools, where it was stored for drinking
and agriculture.
Idaho State University archaeologist Richard Hansen, who is
directing the ongoing excavation,
says that the panels’ carved images depict an important scene from
the Popol Vuh, a text of the Mayan
myth that was first recorded in
the 16th century. In the part of the
story shown, the Hero Twins swim
through the underworld after retrieving the head of their father, the deity
Hun Hunahpu.
Some historians dismiss the Popol
Vuh as a contaminated document,
containing not only ancient Mayan
mythology but also contemporary
Spanish Catholic influences. The
discovery of the panels establishes
key portions of the stories as genuinely Mayan. “We can now extend
the authenticity of the creation myth
back another 1,000 years,” Hansen
says. Sam Kissinger
NUMBERS BY JEREMY JACQUOT
D
R U G S
$228.5
BILLION
Sales of brand-name pharmaceuticals in the
U.S. in 2008, according to the Generic
Pharmaceutical Association’s industry report.
69
Percentage of prescriptions
dispensed in the U.S.
for generic drugs. Generics
account for 16 percent of
total prescription spending.
10-15
Typical number of years needed to develop
a new drug, according to the
Pharmaceutical Research and Manufacturers
of America. A 2007 study estimates
the cost to develop a new medicine at
$1.3 billion (in 2005 dollars).
21$73.9
BILLION
Average amount
spent yearly on
“marketing and
administration” by
10 major pharma-
Number of completely
ceutical firms from
novel drugs (“new 1996 through 2005,
molecular entities”) according to a report
approved by the from the University of
FDA Center for Quebec at Montreal.
Drug Evaluation and During that same
Research in 2008. decade, these
Sixteen were drugmakers spent
approved in 2007, a an average of $28.8
year when 2,742 new
billion annually on
drug compounds R&D, while direct-to-
were under develop- consumer advertising
ment in the U.S. more than tripled.
FROM LEFT: COURTES Y AARON GI TLER/UNIV. OF PENNS YLVANIA; R. D. HANSEN/FARES FOUNDATION/IDAHO S TATE UNIV.; KLAUS GRAMANN & SCO TT MAKEIG/UCSD
Average number of retail
prescriptions per capita
in the U.S. in 2007,
according to calculations
by the Kaiser Family
Foundation, up from 8. 9
a decade earlier.
MILLION
Number of Americans whose drinking water
supplies are known to contain at least
trace amounts of pharmaceuticals, according
to an Associated Press investigation
released last year.
