Biology
is now the study of information stored in DNA - strings of four letters: A, T,
G, and C for the bases adenine, thymine, guanine and cytosine - and of the transformations
that information undergoes in the cell. There were mathematics here? DNA polymerase
is the king of enzymes - the maker of life. Under appropriate conditions, given
a strand of DNA, DNA polymerase produces a second "Watson-Crick" complementary
strand, in which every C is replaced by a G, every G by a C, every A by a T and
every T by an A. For example, given a molecule with the sequence CATGTC, DNA polymerase
will produce a new molecule with the sequence GTACAG. The polymerase enables DNA
to reproduce, which in turn allows cells to reproduce and ultimately allows you
to reproduce. For a strict reductionist, the replication of DNA polymerase is
what life is is all about. DNA polymerase is
an amazing little nanomachine, a single molecule that "hops" onto a
strand of DNA and slides along it, "reading " each base it passes and
"writing" its complement onto a new, growing DNA strand. This was in
similarity to the Turing machine (toy computer) suitable for mathematical investigation
on the study of the notion of "computability" which preceded the advent
of actual computers by about a decade and led to some of the major mathematical
results of the 20th century.
The most striking was that Turing's toy computer
had turned out to be universal and could be programmed to compute anything that
was computable at all. In other words, one could programme a Turing machine to
produce Watson-Crick complementary strings, factor numbers, play chess and so
on. To build a DNA computer, tools were essential
such as (1) Watson-Crick pairing (2) polymerases (3) Ligases (4) Nucleases (5)Gel
electrophoresis, and (6) DNA synthesis.To build a computer, only two things are
really necessary - a method of sorting information and a few simple operations
for acting on that information.
