From Your ORFans Cheerleader
|November 18, 2008||Posted by Paul Nelson under Intelligent Design|
Just a couple of links to enliven your morning…
This Science Daily story describes a paper from the latest PLOS Biology, on the role of ORFans in generating species-specific traits in animals. Konstantin Khalturin and his co-authors at the Christian-Albrechts-University in Germany note the “substantial fraction” of ORFans — genes without known homologs — in every genome thus far sequenced, and argue that the origin of unique morphologies may rest in part with these unique genes:
Understanding the molecular events that underlie the evolution of morphological diversity is a major challenge in biology….All genome and expressed sequence tag (EST) projects to date in every taxonomic group studied so far have uncovered a substantial fraction of genes that are without known homologs. These ‘‘orphans’’ or ‘‘taxonomically restricted genes’’ (TRGs) are defined as being exclusively restricted to a particular taxonomic group. For example, analysis of the phylum Nematoda has identified more than 20% of genes that were nematode-unique TRGs. The draft genome of Ciona intestinalis revealed that nearly one-fifth of the genes were orphans. A comparison between the genome sequences of Schizosaccharomyces pombe and Saccharomyces cerevisiae showed about 14% of the predicted proteins to be unique to Sc. pombe and 19% unique to Sa. cerevisiae. In Drosophila, TRGs include indispensable regulators of development such as bicoid and spätzle. Recent comparative data on the genomes of 12 Drosophila species revealed that about 2.5% of genes are not present outside of the genus Drosophila and, therefore, have most likely arisen de novo. An even larger proportion of lineage-specific genes have been detected in the genome of Tribolium. In bacteria, the cumulative number of orphans identified does not appear to be leveling off, although hundreds of complete genome sequences have been already analyzed. (p. e278, reference numbers omitted)
In their paper, Khalturin et al. examine the role of ORFans in specifying unique anatomical features of two species of the freshwater polyp Hydra. The paper is open access (God bless PLOS; long may it prosper), so go check it out.
To anyone who wishes he or she was born in the 15th century, to take part in the great voyages of discovery: ORFans represent our biological New World. The open vistas of science never end.
(That’s the sort of thing cheerleaders say, you know.)