Information is defined thus: A physical system, or mathematical model of a system which produces a sequence of symbols governed by a set of probabilities is known as a stochastic process. [A]ny stochastic process which produces a discrete sequence of symbols chosen from a finite set may be considered a discrete source of information. Shannon, 1948. More specifically, information is simply a sequence of symbols or in this case molecules that can be represented using symbols, each discrete symbol in the sequence representing a single piece of information, a bit. The four nucleotides of DNA are represented using the symbols A, T, G, and C. Now, take the following hypothetical sequence of DNA: ATCCTGAGAC There are 10 nucleotides in this sequence, and thus there are 10 pieces of information or bits in this sequence. Now, say a mutation occurs in which several nucleotides are inserted into the sequence, known as an addition mutation: ATC AAA CTG AGAC The sequence has increased by three bases, and thus now contains 13 pieces of information or bits. A more dramatic example of increases in information within a species is when one or more entire chromosomes are duplicated, which is very common in plants, less so in animals but not unheard of. It that case you have an enormous case of functional redundancy, with the duplicate chromosome free to undergo mutations that otherwise might well have proved fatal to the organism, but since it now has an extra copy of those essential genes, the negative selection pressure against mutants of those genes has been relieved. So in this case, you have an entire chromosomes worth of information added to the organism, which then spreads among the population. talkorigins.org/origins/postmonth/jan99.html
Posted on: Sun, 16 Mar 2014 20:27:36 +0000
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