Bruce A. Martin
About 1200 words
Computers are binary; so is life.
In the story of Noah, all the animals were organized in pairs. This, of
course had nothing to do with contemporary computer requirements, but was
more due to the existence of two sexes. However, the binary nature of life
goes far deeper than the number of genders and gamates. A closer look reveals
that Biology has more in common with computer circuitry than we may think.
Modern computers are built up from microscopic electronic elements, each
of which can be either "on" or "off", like a light bulb or a light switch.
Because each element must be in one or another "state" - not both, and never
something else - it is convenient to use a "binary" number system, where
there are only two digits: zero and one. Such a system was devised nearly a
century before the first electronic computer was built, by George Boole
(whose last name almost appears to contain two zeroes and a one!).
Now, a binary view of the world seems quite natural, even obvious for
certain things like:
as well as electronic currents and circuits.
- RSVP responses
- male or female
- Yin & Yang
- stop/go traffic lights
- up/down staircases
- true/false questions
- toilet flush handles
- door locks
- warning lights
- on/off switches
What is far less obvious is how
the basic building blocks of all life (on Earth, at least) also seem to
adhere to a binary paradigm in many of their details and mechanisms.
Long after Boole's invention of the binary number system (and somewhat
after the first real computers were assembled out of relays, at places like
Los Alamos, in the 1940s), Biologists began to unravel and explore the way
that living cells preserve and use the information which they and their
offspring will need in order to grow and function. All animals and plants,
in nearly all of their living cells, contain a complete set of plans kept in
storage mechanisms which we call "genes" and "chromosomes". Before anyone
attempts to feed a bunch of chromosomes into a tape reader or floppy drive,
or begins translating a DNA into ASCII code, it must be pointed out that the
genetic information is NOT coded in bits and bytes. (Nor is the data stored
as magnetic domains or laser spots!) However, the fundamental structure of
this data has more of a binary basis than one might imagine.
Animals and plants, and the organs they contain, are literally assembled
by making combinations of amino acids that must arrive in a precise sequence,
to be combined correctly. The process is somewhat like having a blind person
assemble a "Lego" (or Tinker Toy) model by having the correct block magically
produced and handed to him exactly at the right time, just when his hand
touches the spot where it is to be added on. The precise sequence of amino
acids that will create the next required component (protein, enzyme, or
whatever) is contained within a "gene", which is usually a very small portion
of one of the several "chromosomes" that are preserved within the tiny nucleus
of a microscopic cell.
Now, the amino acids themselves are not stored in the genes -- there's not
enough room for the material itself. What is stored is only the information.
The difference in size is similar to the difference between a book of animals
and a zoo, or between a bankbook and a bank vault. Computers store information
in tiny, even microscopic spaces, but the reality represented by that information
can be huge - as when a chart of the stars is stored in a microchip. Since a
miniscule cell contains the complete set of plans for the entire animal, there
is a similarity to the storage of information in a computer, but the resemblance
doesn't stop there, and while the method of storage is very different there is
a fundamental binary basis to both.
The chromosomes come in pairs, of course, but that's merely because one
of one of each pair is contributed by each of the two parents. But, in most
animals, each chromosome of the pair consists of a pair of structures called
"Chromatids", usually joined together near the middle (by a "centrosome") so
that the whole thing appears somewhat like a sloppily drawn letter "X". Each
of the chromatids (i.e. two in each of the two chromosomes of the pair) is
composed of two strands of a certain chemical called de-oxy-Ribonucleic Acid,
popularly known as DNA. The two strands of DNA twist together and spiral
around each other like a pair of entangled Slinky toys, to form what has come
to be called a "double helix".
The actual "codes" (which control the amino acid sequencing) come from
little connecting links that go between the two DNA strands. These links
look very much like rungs on a (twisty) ladder. There are two different
kinds of ladder rung. The ladder rungs themselves are built up out of pairs
of chemicals we'll call A, T, C, and G (short for some longer chemical names
which don't matter here). As you might expect, by this time, there are only
two possible types of ladder rung: One type of ladder rung has an "A" on one
end and a "T" on the other end; the second type has a "C" on one end and a
"G" on the other end. This is because, while the A, T, C, and G ends fit
equally well into the DNA strands that surround them, an A only holds hands
with a T, a C will only hook up with a G. A-G or C-T just won't work (and
you'd fall off a ladder whose steps broke in the middle!). Furthermore, no
self-respecting A, T, C, or G would ever consider joining up with another of
the same type.
Therefore, there are only two types of ladder rung. However, there are
two ways that an A-T can be arranged, and two ways that C and G can appear.
If there is a C on one side, there is sure to be a G opposite it. But there
could be a G with a C opposite it. Likewise for A-T or T-A.
To recap, and to paraphrase the bard badly, one might ask: "How do I life
thee? Let me count the ways. Starting from the inside out, we have:
which you got from your two parents.
- 2 different ways to arrange each of the
- 2 different kinds of ladder rung, to link the
- 2 strands of DNA that make up each of the
- 2 Chromatids in each of the
- 2 chromosomes in each pair
And the animals marched aboard the Ark two by two.
Thus, the basic building block of life is organized in a binary fashion,
at each level. The rungs of the ladder carry the information to specify the
building sequence. Since there are four different types of ladder rung, we
may say that a computer could specify the same information with "two bits" --
which is an old slang expression for twenty-five cents.
END OF MAIN ITEM.
ADDITIONAL PIECE FOLLOWS.
(About 125 words)
How much is a bit worth, in real money?
Before Thomas Jefferson introduced decimal coinage in the United States,
a very commonly found coin, often used in trade, was the old Spanish Dollar
(or Maria Theresa Thaler, picturing the Empress). To make change, this soft
coin was often cut in half, halved again, and even halved a third time to
make "pieces of eight". This is the origin of the slang two "two bits",
referring to the American quarter.
By the way, there is a weak pun in the title, since the "Real" is an old Spanish
unit of currency. Really. In fact, it still survives in parts of Latin
America. In some countries, a Real is worth one-eight of a Peso -- that's
really a bit of change.
© 2000, Bruce A. Martin
P.O.Box 456, Middle Island, NY 11953