The book of life?

Since the release of the first human reference genome it becomes clearer that the analogy of the genome as the “book of life” (see wikipedia of “genome”) was misleading. While its chapters, paragraphs and footnotes are still elusive, the evidences suggest that genomes of multi-cellular eukaryotes encode information in much more complex ways. The book analogy emerged in the early days of genomics when genes were thought to be the major informative part of the genome. The analogy seemed proper because the open reading frame resembles a sentence of a natural language. The “reading direction” is from the 5’ to 3’ and the genetic code well defines the slightly redundant transformation from codons to amino acids. A stop codon marks the 3’ end of the reading frame like a dot in the end of sentence. Regulatory codes of the single cellular prokaryotes and yeasts supported this notion (e.g. the lac operon, his3). However, new discoveries from higher eukaryotes suggest that the organization of the regulatory codes is more complex. First, the definition of the basic information units is usually not pronounced (no “words”). Second, the information is shuffled without defined linear directionality (no “reading direction”). Third, multiple unrelated functions (“meanings”) can be multiplexed with no defined syntax (no “sentences”). Above all, regulatory encodings of eukaryote genomes may be highly redundant5. In a retrospective view, we could not really expect multi-cellular organisms to have simple grammar regulatory codes.