Genome Complexity; immunity is Lamarkian (Introduction)

by David Turell , Tuesday, January 27, 2015, 14:43 (3589 days ago) @ David Turell

In the so-called junk DNA areas many immune battle weapons are formed and used:-http://www.the-scientist.com//?articles.view/articleNo/41702/title/A-Movable-Defense/-"Researchers now recognize that genetic material, once simplified into neat organismal packages, is not limited to individuals or even species. Viruses that pack genetic material into stable infectious particles can incorporate some or all of their genes into their hosts' genomes, allowing remnants of infection to remain even after the viruses themselves have moved on. On a smaller scale, naked genetic elements such as bacterial plasmids and transposons, or jumping genes, often shuttle around and between genomes. It seems that the entire history of life is an incessant game of tug-of-war between such mobile genetic elements (MGEs) and their cellular hosts.-"MGEs pervade the biosphere. In all studied habitats, from the oceans to soil to the human intestine, the number of detectable virus particles, primarily bacteriophages, exceeds the number of cells at least tenfold, and maybe much more. Furthermore, MGEs and their remnants constitute large portions of many organisms' genomes—as much as two-thirds of the human genome and up to 90 percent in plants such as corn.-"Despite their ubiquity and prevalence in diverse genomes, MGEs have traditionally been considered nonfunctional junk DNA.--"The two independent origins of adaptive immune systems in prokaryotes and eukaryotes involving unrelated MGEs show that, in the battle for survival, organisms welcome all useful molecular inventions irrespective of who the original inventor was. Indeed, the origin of CRISPR-Cas systems from prokaryotic casposons and vertebrate V(D)J recombination from Transib transposons might appear paradoxical given that MGEs are primary targets of immune systems. However, considering the omnipresence and diversity of MGEs, it seems likely that even more Lamarckian-type mechanisms have, throughout the history of life, directed genomic changes in the name of host defense.16-"Moreover, the genome-engineering capacity of immune systems provides almost unlimited potential for the development of experimental tools for genome manipulation and other applications. The utility of antibodies as tools for protein detection and of RM enzymes for specific fragmentation of DNA molecules has been central to the progress of biology for decades. Recently, CRISPR-Cas systems have been added to that toolkit as, arguably, the most promising of the new generation of molecular biological methods. It is difficult to predict what opportunities for genome engineering could be hidden within still unknown or poorly characterized defense systems."