A mutation is a random unintentional change of the genome. However,
if the changes we detect are not randomly distributed, they are not
mutations at all, but more likely a change produced intentionally
through genetic recombination.
Darwin In the Genome: As evidence builds up from studies of the
genomes of various species, it's beginning to seem that mutations
aren't always random: they occur more often in some genes than in
others. Genes that make proteins involved in the simple chores of
cellular housekeeping can be virtually identical in widely different
species. But those that may give a selective edge - such as those
coding for the toxins used by predatory sea snails to catch their
prey - change rapidly from generation to generation. In Darwin in the
Genome, Lynn Caporale explains the many ways that organisms shuffle
the DNA pack to deal a winning hand. The nomadic chunks of DNA known
as transposons and even the repeat sequences once dismissed as "junk"
now seem to be mechanisms for generating this genetic variety, she
says. Caporale, a biotechnology consultant working in New York,
subtitles her book "Molecular strategies in biological evolution",
but rejects any suggestion that its contents undermine classical
Darwinian theory. The term "strategy" is not used to imply that the
process is driven by a preordained plan, as creationists would argue.
Rather, she says, it is used to indicate mechanisms that "have the
effect of anticipating and responding to challenges and opportunities
that continue to emerge in the environment".