The elusive concept of the gene.
In recent years geneticists have witnessed many significant observations which have seriously shaken the traditional concept of the gene. These specifically include the facts that (1) the boundaries of transcriptional units are far from clear; in fact, whole chromosomes if not the whole genome seem to be continuums of genetic transcription, (2) many examples of gene fusion are known, (3) likewise many examples of so-called encrypted genes are known in the organelle genomes of microbial eukaryotes and in prokaryotes, and (4) in addition to the structure of the gene, its functional status can also be inheritable, and, further, (5) epigenetic extra-genomic modes of inheritance, called genetic restoration, seem to be a rather common phenomenon, meaning that organisms can sometimes rewrite their DNA on the basis of RNA messages inherited from generations past. I will briefly review these observations and discuss the difficulties of defining the gene, and then formulate a new view, which is called the relational or systemic concept of the gene. It has to be noted that genes assume their information content characteristics in the Shannonian sense as nucleotide sequences of DNA (or RNA). However, on the basis of this we cannot say anything about their information content in the semantic sense. The semantic information content of genes is context-dependent. Genes namely assume their biochemical characteristics usually only within living cells, their developmental characteristics only within living organisms, and their evolutionary characteristics only within populations of living organisms.
Portin
Petter
P
Laboratory of Genetics, Department of Biology, University of Turku, Turku, Finland. petter.portin@utu.fi
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D005057:Eukaryotic Cells; D019143:Evolution, Molecular; D005796:Genes; D016678:Genome; D016680:Genome, Bacterial; D015894:Genome, Human; D006801:Humans; D014158:Transcription, Genetic
D004247:DNA