DNA MESSAGES

Cliff Pickover cliff at WATSON.IBM.COM
Thu Oct 17 11:27:23 EST 1991


The following paragraphs will no doubt seem silly to most mathematicians
and biologists, so serious readers will wish to skip this posting.  If
you are interested, I'd be curious as to your answers to the few
questions which are highlighted in CAPITAL letters.  I am interested in
the coding and information aspects of these questions.  You may send
your ideas and comments directly to me, if you wish.  This might
avoid cluttering the bulletin board with postings which some
readers may wish to avoid due to their speculative nature.
cliff @  watson.ibm.com

DNA MESSAGES

   It's easy to imagine a science-fiction plot where
a scientists sequencing the hereditary material of life (DNA) notes that
it encodes a message.  The DNA sequence, expressed as a four letter code
using the symbols G, C, A, and T, could code for practically anything.
For example, it could contain the value for pi (3.1415...).  HOW MANY
DECIMAL DIGITS OF PI ENCODED IN DNA WOULD IMPRESS A SCIENTIST AS
SOMETHING SPECIAL?  After all, just a few digits could occur simply by
chance.  A few hundred digits might make a scientist gasp in shock.

   Astronomers for years have scanned the heavens for radio messages
from alien creatures.  IF YOU WERE AN ALIEN CREATURE TRYING TO CODE A
MESSAGE USING THE FOUR SYMBOLS (G, C, A, AND T), HOW WOULD YOU DO IT,
AND WHAT MESSAGE WOULD YOU ENCODE?

   The idea of placing messages in genetic sequence is not
entirely fanciful.  Joe Davis at MIT hopes to place encoded messages in
the DNA of a bacteria which could duplicate and spread through the
galaxy.  His collaborator, Dana Boyd, a geneticist from Harvard, has
synthesized a short sequence of DNA consisting of 47 base pairs with a
brief coded message.  When converted to a grid of binary digits, the
message appears as a sketch of the female genitalia.  100 million copies
of this message have been stored in a vial.  Of course Davis and
colleagues do not really plan to disperse these bacterial spores, but
Davis has noted that this "may be the only practical way for humans to
explore the cosmos."

   USING JUST THE 4 SYMBOLS G, C, A, AND T, WHAT ARE SOME WAYS
YOU CAN THINK OF FOR CODING MESSAGES FOR TRANSMISSION INTO OUTERSPACE?




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