Genome Complexity; making immune complexes (Introduction)

by David Turell , Tuesday, January 06, 2015, 23:45 (3609 days ago) @ David Turell

Very complex movements of transposons and other elements (CRISPR) make fresh antibodies against new invaders. This stuff in DNA previously was so-called junk, but isn't:-" Combined with a detailed analysis of the predicted functions of Cas proteins, this discovery led one of us (Koonin) and his team to propose in 2006 that CRISPR-Cas functioned as a form of prokaryotic adaptive immunity, with memory of past infections stored in the genome within the CRISPR “cassettes”—clusters of short direct repeats, interspersed with similar-size nonrepetitive spacers, derived from various MGEs—and to develop a detailed hypothesis about the mechanism of such immunity.-"Subsequent experiments from Philippe Horvath's and Rodolphe Barrangou's groups at Danisco Corporation,along with several other studies that followed in rapid succession, supported this hypothesis. (See “There's CRISPR in Your Yogurt,” here.) It has been shown that CRISPR-Cas indeed functions by incorporating fragments of foreign bacteriophage or plasmid DNA into CRISPR cassettes, then using the transcripts of these unique spacers as guide RNAs to recognize and cleave the genomes of repeat invaders. (See illustration.) A key feature of CRISPR-Cas systems is their ability to transmit extremely efficient, specific immunity across many thousands of generations. Thus, CRISPR-Cas is not only a bona fide adaptive immunity system, but also a genuine machine of Lamarckian evolution, whereby an environmental challenge—a virus or plasmid, in this case—directly causes a specific change in the genome that results in an adaptation that is passed on to subsequent generations. (my bold)-http://www.the-scientist.com/?articles.view/articleNo/41702/title/A-Movable-Defense/