Monday, July 6, 2009

Werner Arber - Gwildor of Molecular Biology

ResearchBlogging.orgThe locksmith that uncovered the keys to genetic manipulation - Wener Arber - expressed some of his thoughts on the nature of natural selection last week at the Annual Meeting of Nobel Laureates at Lindau, Gernamy. P.Z. Meyers at Pharyngula critically reviews his synthesis and takes a particularly skeptical view of his conclusions.

The main conclusion Arber makes is that genomes contain a duality of genes that affect mutation rates and therefore the rate of evolution. On one hand there are genes that "benefit individuals for the fulfillment of their lives" and on the other hand there are genes that "act to the benefit of an evolutionary development, for a slow, but steady expansion of life and biodiversity." Arber is saying that there are parts of all genomes that actively promote variation but at the same time there are also those that maintain the happy status quo. He calls the former "evolution genes" - this terminology might come off as a little sweeping and inappropriate but I have a proposed explanation coming up. PZ has a problem with this because he says there is not evidence for the existence of genes "that will only help an individual's many-times-great-grandchildren."

This is where my thoughts came rushing in. For some random reason last week I was reading various online biographical sketches of Barbara McClintock - the Nobel Prize winning scientist who discovered "jumping genes" aka transposons - these are genetic sequences that can "cut and paste" themselves around the genome's geography. She demonstrated that 50% of the Zea Maize genome is comprised of transposable elements. That is one highly variable genome! She spent a large part of her career studying the evolution of the corn plant and made some profound observations about the nature of the genome before the structure of DNA was even known. I digress. I propose that these transposable genetic elements are the very "evolution genes" that Arber is talking about. Consider that some transposons have heat-shock like promoters (for non-scientists - promoters are like genetic bookmarks that tell the cell which pages of the blue-prints to read in order to build the cell's machinery). Heat shock promoters become engaged when a cell is subjected to stress- starvation, extreme heat, cold, etc. etc. It has been proposed in the literature that increased rates of mutation due to increased rates of transposition may be beneficial to a population of cells under environmental stress1. Thus if the environment is pleasant "status quo genes" are free to maintain a steady biological state, whereas in changing environmental conditions the "evolution genes" can come out of dormancy, even after epochs, to save the day.

In the end PZ criticizes Arber's talk saying that it really doesn't bring any new ideas to the table. Well I have noticed that the blogging-heads mentality of new new new everything really does not allow us to reflect and reorganize old knowledge in possibly useful ways. The point Arber is making really builds an accompanying theme to the premise of Dawkins' the Extended Phenotype. In that book Dawkins explains how genetic instructions intertwine with the non-living environment through behavior modulation. Arber is saying that the non-living environment ultimately and actively directs the course of evolution through activation of variability-promoting genes (even though variation is usually detrimental). I think PZ was initially confused in thinking that Arber was assigning some kind of higher direction to that non-living "natural reality."

1.Strand, D., & McDonald, J. (1985).
is transcriptionally responsive to environmental stress
Nucleic Acids Research, 13 (12), 4401-4410 DOI: 10.1093/nar/13.12.4401

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