IX DNA SEQUENCE EVOLUTION
Most biologically important information, i.e. information that determines the phenotype of the organism, is encoded in the nucleic acid sequence (DNA in most organisms).This information is translated to phenotype of an organism to a major degree through proteins, which are synthesized on the basis of information encoded in the DNA.Consequently, evolution of the phenotype of organisms is closely linked to the evolution of nucleic acids.It can be stated with an acceptable degree of simplification that every evolutionary change that occurs at the level of an organism is accompanied by a change at the level of the nucleic acid.Although the evolution of the phenotype and the evolution of the nucleic acid thus occur in parallel, the mechanisms that operative in both processes and some phenomena that occur during their progress differ in certain respects.The methods employed to study these two processes also differ fundamentally.Consequently, a separate chapter is devoted to the evolution of nucleic acids.The subject of mutation bias, reparation drive and molecular drive would also belong in their contents, as would, to a certain degree, the subject of genetic drift.However, separate chapters were devoted to these areas. A separate chapter is also devoted to the subject of the use of molecular biological traits in taxonomy and phylogenetics.
As the genome of most organisms consists of DNA, while RNA plays the role of the bearer of genetic information only in some viruses, for simplicity this chapter will refer only to DNA and not to nucleic acid (or “DNA or RNA”).The described laws of the evolution of DNA are, of course, equally valid for the evolution of RNA in viruses with an RNA-genome.