Canal-U

3.10. Gene prediction in eukaryotic genomes

If it is possible to have verygood predictions for bacterial genes, it's certainly not the caseyet for eukaryotic genomes. Eukaryotic cells have manydifferences in comparison to prokaryotic cells. You rememberthe existence of a nucleus and you also remember on one ofthe schemes in the first week that there are more structureswithin a eukaryotic cell. But the differences lie also inthe organization of the genomes. In eukaryotic genomes, the so-calledintergenic regions are very long. Intergenic regions are theregions which separate genes. A bacterial genome is very denseindeed, if you put your fingers somewhere on the genome, if itwas possible of course, it would be on the gene. If you do the sameon a eukaryotic genome, the probability is very very very highthat it is on an intergenic region. Indeed if you take the exampleof the human genome, less than 5% of the sequences of a human genome are made up of genes, 95 % of the humangenomes are not genes. What are they? This isstill an open question. Years ago a biologist spoke about germDNA to say, well DNA which is useless. Now the feeling is somewhat different,it certainly has a reason to exist. We understand some of thesereasons but not all.