Molecular Biology, enunciated by Francis Crick (one of the co-discoverers of
the double-helix structure of DNA):DNA :::;, RNA :::;, proteins.It is my hope that with this very skeletal model I have constructed the
reader will perceive some simple unifying principles of the field-
principles which might otherwise be obscured by the enormously intricate
interplay of phenomena at many different levels. What is sacrificed is, of
course, strict accuracy; what is gained is, I hope, a little insight.Strands, Bases, EnzymesThe game of Typogenetics involves typographical manipulation on se-
quences of letters. There are four letters involved:A C G T.Arbitrary sequences of them are called strands. Thus, some strands are:GGGG
ATTACCA
CATCATCATCA1Incidentally, "STRAND" spelled backwards begins with "DNA". This is
appropriate since strands, in Typogenetics, play the role of pieces of DNA
(which, in real genetics, are often called "strands"). Not only this, but
"STRAND" fully spelled out backwards is "DNA RTS", which may be taken
as an acronym for "DNA Rapid Transit Service". This, too, is appropriate,
for the function of "messenger RNA"-which in Typogenetics is rep-
resented by strands as well-is quite well characterized by the phrase
"Rapid Transit Service" for DNA, as we shall see later.
I will sometimes refer to the letters A, C, G, T as bases, and to the
positions which they occupy as units. Thus, in the middle strand, there are
seven units, in the fourth of which is found the base A.
If you have a strand, you can operate on it and change it in various
ways. You can also produce additional strands, either by copying, or by
cutting a strand in two. Some operations lengthen strands, some shorten
them, and some leave their length alone.
Operations come in packets-that is, several to be performed together,
in order. Such a packet of operations is a little like a programmed machine
which moves up and down the strand doing things to it. These mobile
machines are called "typographical enzymes"--enzymes for short. Enzymes
operate on strands one unit at a time, and are said to be "bound" to the unit
they are operating on at any given moment.
I will show how some sample enzymes act on particular strings. The
first thing to know is that each enzyme likes to start out bound to a
particular letter. Thus, there are four kinds of enzyme-those which prefer
Self-Ref and Self-Rep 505