Edward Rubin again finds hard evidence supporting a front loaded evolution. Front loading is a design engineering term generally used to describe design elements inserted for possible use in the future (contingency) as opposed to immediate use. The mechanism of random mutation and natural selection is incapable of contingency planning. RM+NS can build based on experience but can’t build based on an abstract future. It is reactive not proactive. The front loading hypothesis in essence says the complex specified information necessary to construct the more complex machinery of life has been around since life appeared on the earth but much of it was preserved for expression in the far distant future. Natural selection cannot preserve unexpressed information for long against the onslaught of random mutation. What’s unimportant for survival mutates into random junk or is deleted altogether. Thereby the RM+NS theory predicts that any DNA sequences that are preserved, mostly or entirely unchanged, for tens and hundreds of millions of years must be very important for survival and reproduction. The most serious objection to evolution (phylogenesis) being a front loaded process is that there is no known mechanism that can preserve unexpressed DNA for long periods of time. A front loaded phylogeny can be compared to ontogeny (the process of a single organism going from egg to adult) except that phylogeny takes many millions of years for the diversification of a single cell into many specialized cells and organisms whereas individual organisms go from one cell to many very specialized cells and organs in a matter of days or weeks. Phylogenesis is no more dependent on random chance for what it produced than ontogeny is dependent on chance – both have a predetermined course of action.
Rubin and his research have turned up compelling evidence that there is some unknown mechanism (something other than natural selection) which is working to preserve genomic information for geologic periods of time. We blogged Rubin’s last experiment where millions of highly conserved (75%-95% sequence similarity) DNA base pairs were deleted from a mouse with no observed deleterious effect on the genetically modified progeny. Below is the abstract and author summary from his latest paper in this area of research where four ultraconserved (95% – 100% sequence similarity) DNA regions were deleted. Click the link below to read the whole paper. My emphasis added in bold where the authors express surprise. These results are no surprise to front loading pundits, that’s for sure.
Nadav Ahituv, Yiwen Zhu, Axel Visel, Amy Holt, Veena Afzal, Len A. Pennacchio, Edward M. Rubin
Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States Department of Energy Joint Genome Institute, Walnut Creek, California
PLoS Biology: September 4, 2007
Ultraconserved elements have been suggested to retain extended perfect sequence identity between the human, mouse, and rat genomes due to essential functional properties. To investigate the necessities of these elements in vivo, we removed four noncoding ultraconserved elements (ranging in length from 222 to 731 base pairs) from the mouse genome. To maximize the likelihood of observing a phenotype, we chose to delete elements that function as enhancers in a mouse transgenic assay and that are near genes that exhibit marked phenotypes both when completely inactivated in the mouse and when their expression is altered due to other genomic modifications. Remarkably, all four resulting lines of mice lacking these ultraconserved elements were viable and fertile, and failed to reveal any critical abnormalities when assayed for a variety of phenotypes including growth, longevity, pathology, and metabolism. In addition, more targeted screens, informed by the abnormalities observed in mice in which genes in proximity to the investigated elements had been altered, also failed to reveal notable abnormalities. These results, while not inclusive of all the possible phenotypic impact of the deleted sequences, indicate that extreme sequence constraint does not necessarily reflect crucial functions required for viability.
It is widely believed that the most evolutionarily conserved DNA sequences in the human genome have been preserved because of their functional importance and that their removal would thus have a devastating effect on the organism. To ascertain this we removed from the mouse genome four ultraconserved elementsÃ¢â‚¬â€sequences of 200 base pairs or longer that are 100% identical among human, mouse, and rat. To our surprise, we found that the mice lacking these elements are viable, fertile, and show no apparent abnormalities. This completely unexpected finding indicates that extreme levels of DNA sequence conservation are not necessarily indicative of an indispensable functional nature.
HT to Jehu for recognizing the importance of the paper for front loading and bringing it to my attention.