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Science
Friday > Archives
> 1998
> December
> December 18, 1998:
Hour One: Animal Genome Sequenced / A Perfect Mirror
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Last week came a monumental development that you
might have missed. For the first time ever,
scientists have sequenced the entire genome of an
animal. It's been a busy year in biological science
- seems like every week there's another gene
discovered or another something cloned. The Human
Genome Project continues to step along towards
sequencing the entire human genetic code, and
earlier efforts have sequenced the genome of some
single-cell organisms and yeasts. But the
sequencing of the entire genome of an animal, even
a simple one, promises to change genetic research
around the world.
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Image courtesy Genetics
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The animal, a roundworm called C. elegans, is
microscopic, yet is thought to have over nineteen thousand
genes containing some ninety-seven million DNA base pairs.
Over the ten years that it has taken two groups of
biologists to complete the worm genome sequence, they have
gradually been posting their results on the internet. Their
findings have been used by scientists working on other
projects for comparison - and surprisingly, many scientists
working on the human genome have discovered that some human
genes are quite similar to those in worms. Discovering a
gene's purpose in the relatively simple worm, then, can give
information about possible uses of that gene in humans.
Discoveries about aging, Alzheimer's disease, and some forms
of cancer have come out of the C. elegans genome
research.
Join us on this segment of Science Friday for a conversation with one
of the scientists responsible for this wormy yet wondrous accomplishment.
And then...
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Most mirrors- like most people - aren't perfect. There are two
types of mirrors, metallic and dielectric, and both have shortcomings.
But a group of physicists and materials scientists at MIT say
that they have invented a new kind of mirror that combines the
best qualities of both kinds of mirror, without the drawbacks.
They're calling it a "perfect" mirror.
Metallic mirrors, like the one hanging on your bathroom wall,
can reflect a wide range of wavelengths of light - the reflection
of a red shirt shows up just as well as the reflection of a green
shirt. Metallic mirrors also work across many angles - you don't
need to stand at a very precise position in the bathroom in order
to show up in the mirror. However, because the metallic particles
in the mirror absorb some of the light energy striking them, reflections
off metallic mirrors are usually a few percent dimmer than the
original image.
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There's another type of mirror, called the dielectric mirror, that doesn't
absorb very much light at all. The mirrors, found mainly in laboratories,
are made from alternating layers of different transparent, nonconductive
materials. Light reflects off the interface between the layers of materials,
but only at certain angles - and some wavelengths reflect better than
others.
The MIT researchers created a mirror that combines parts from both
types of mirrors, sandwiching alternating micron-thick layers of shiny
tellurium with layers of polystyrene (the plastic in plastic wrap).
The scientists say that their new mirror design could have many applications
in technology. Imagine flexible tubes that could carry light miles for
communications with no amplifiers and no loss of power. Imagine windows
coated with a transparent mirror that is "tuned" to reflect only infrared
(heat) radiation - so visible light would come in, but heat would stay
out. Or imagine an optical trap that could hold light longer than any
other, allowing scientists to study its properties better. Sound amazing?
We'll find out more.
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The Mirror Matrix
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Mirror type
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works at which angles?
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reflects which wavelengths?
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energy loss?
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metallic
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many
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many
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high: several percent
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dielectric
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few: best straight-on
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few
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very low
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"perfect"
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many
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many
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very low
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Guests:
Robert Waterston
Chairman, Genetics Department
Washington University
St. Louis, MO
John Joanoppoulus
Francis Wright Davis Professor of Physics
Massachusetts Institute of Technology
Cambridge, MA
Yoel Fink
Graduate Student
Massachusetts Institute of Technology
Cambridge, MA
Books/Articles Discussed:
"C. elegans: Sequence To Biology". Special Section, Science
Magazine, Dec 11, 1998.
"A Dielectric Omnidirectional Reflector" by Y. Fink, J. N. Winn, S.
Fan, C. Chen, J. Michel, J.D. Joannopoulos, E. L. Thomas. Science
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November 27, 1998.
Related Links:
Genome Sequencing
Center: Notes associated with the 1998 Science Paper
The C. elegans server at the University
of Texas Southwestern Medical Center
MIT press
release on the mirror technology
This segment produced by:
Annette Heist
Web producer:
Charles Bergquist
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