Number 202, November 9, 1994 by Phillip F. Schewe and Ben Stein
SO-CALLED "JUNK" DNA , regions of genetic material (accounting
for 97% of the human genome) that do not provide blueprints for proteins
and therefore have no apparent purpose, have been puzzling to scientists.
Now a new study shows that these non-coding sequences seem to possess structural
similarities to natural languages. This suggests that these "silent"
DNA regions may carry biological information, according to a statistical
analysis of DNA fragments by researchers at Boston University and Harvard
Medical School (contact H.E. Stanley of Boston University, 617-353-2617).
Studying DNA sequences from humans, viruses, bacteria, yeast, and other
organisms, the researchers performed statistically-based linguistics tests
on the 37 known DNA sequences each having at least 50,000 "base pairs"
or "letters" of DNA code. The researchers first performed a variation
of a test known as Zipf analysis, in which the words from a text are arranged
on an x-axis from most frequently occurring to least frequently occurring;
plotted against their rank is the actual number of occurrences of that
word in the text. For natural languages one invariably gets a straight
line (on a graph using logarithmic axes) whose slope is about -1. The non-coding
DNA sequences had linear slopes when base pairs were grouped into genetic
"words" consisting of 3, 6, 7, or 8 base pairs. Interestingly,
the slope values for non- coding sequences were closer to -1 than for coding
DNA, supporting a hypothesis that protein- coding DNA may be more like
a compressed computer file than a natural language. (R.N. Mantegna et al.,
upcoming article in Physical Review Letters.)
A NEARBY LARGE SPIRAL GALAXY not previously noted has been discovered
by astronomers using a telescope, the Dwingeloo radio telescope in Holland,
dedicated to searching for galaxies hidden behind the disk and dust of
our own galaxy. The new galaxy, called Dwingeloo 1, is about 10 million
light years away. Unlike the dwarf galaxy found earlier this year in orbit
around (and behind) the Milky Way (see Update 174), Dwingeloo 1 is a large
galaxy and is not considered part of our local group of galaxies. The new
observations are part of a program to study a neglected part of the sky,
a region aptly called the "Zone of Avoidance" because astronomers
scanning extragalactic space had heretofore steered their telescopes away
from the haze of foreground stars constituting our galaxy. (R.C. Kraan-Korteweg
et al., Nature, 3 Nov. 1994; this is Nature's 125th anniversary issue;
Happy Birthday.)
WHAT HAPPENED TO THE SSC STAFF? A year after Congress shut down the
nascent supercollider, the number of scientists and technicians on the
staff has dropped from 1100 to less than 100. About a fourth are jobless.
Some have returned to academe. Former SSC director Roy Schwitters is now
a physics professor at the University of Texas. About half of those who
have found jobs are working outside particle physics. Some examples: Cas
Milner, who had worked on the Gamma-Electron-Muon (GEM) detector at the
SSC, now works at the TIAA-CREF pension fund. Kate Morgan (also formerly
with GEM) moved on to Citicorp. (Science, 28 October 1994.)
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