Information Technology Reference
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truly functional genotype/phenotype system that can be easily implemented
using any programming language, as nothing in this algorithm depends on
the workings of a particular language.
1.2 Biological Gene Expression
Of the information stored in DNA molecules, what most interests us are the
genes coding for proteins. In eukaryotes, an average of only 2% of the ge-
nome codes for proteins, whereas the rest is mainly repetitive sequences and
introns (noncoding sequences that interrupt the coding sequences of genes).
The genomes of prokaryotes and virus are, however, much more compact
and they are essentially organized in genes that code for proteins. For our
purpose it is enough to have in mind the simplest genomes, since they are
already extremely complex life machines.
1.2.1 Genome Replication
When in 1953 James D. Watson and Francis Crick proposed the model for
the double helix, the mechanism of DNA replication became obvious to all,
and it was only a matter of time to isolate and study the essential participants
and understand the details of the mechanism. The complementary, double-
stranded DNA molecule opens itself and each strand serves as template for
the synthesis of the respective complementary strand (Figure 1.2). For in-
stance, when a virus replicates within a cell, it copies its genome hundreds of
times, forming hundreds of new virions in a few minutes.
As fundamental as it is in biology (not only in DNA replication but also in
DNA repair), the double-stranded nature of DNA molecules is of little use to
replicate the genomes in a computer system such as GEP or GAs, where
single-stranded chromosomes are copied using simple computer instructions.
More important to us are the modifications that allow the creation of genetic
diversity. In the next section, I will briefly introduce the fundamental mecha-
nisms of genetic variation.
1.2.2 Genome Restructuring
In the cell, the processes of information restructuring are related to different
functions, like, for instance, response to environmental stresses, repair of
