@Leadfoot,
There is ascientific pushback on the word "functional" . It seems that a major event of determining whether the 80% number is factual or local. The interspecies ENCODE is underway to look at genomes of drosophila and musca to wee what strands were functional and on what means.
Quote: Although the consortium claims they are far from finished with the ENCODE project, many reactions to the published papers and the news coverage that accompanied the release were favorable. The Nature editors and ENCODE authors "... collaborated over many months to make the biggest splash possible and capture the attention of not only the research community but also of the public at large". The ENCODE project's claim that 80% of the human genome has biochemical function was rapidly picked up by the popular press who described the results of the project as leading to the death of junk DNA
However the conclusion that most of the genome is "functional" has been criticized on the grounds that ENCODE project used a liberal definition of "functional", namely anything that is transcribed must be functional. This conclusion was arrived at despite the widely accepted view, based on genomic conservation estimates from comparative genomics, that many DNA elements such as pseudogenes that are transcribed are nevertheless non-functional . Furthermore the ENCODE project has emphasized sensitivity over specificity leading possibly to the detection of many false positives.Somewhat arbitrary choice of cell lines and transcription factors as well as lack of appropriate control experiments were additional major criticisms of ENCODE as random DNA mimics ENCODE-like 'functional' behavior.
In response to some of the criticisms, other scientists argued that the wide spread transcription and splicing that is observed in the human genome directly by biochemcial testing is a more accurate indicator of genetic function than genomic conservation estimates because conservation estimates are all relative and difficult to align due to incredible variations in genome sizes of even closely related species, it is partially tautological, and these estimates are not based on direct testing for functionality on the genome.
Conservation estimates may be used to provide clues to identify possible functional elements in the genome, but it does not limit or cap the total amount of functional elements that could possibly exist in the genome. Furthermore, much of the genome that is being disputed by critics seems to be involved in epigenetic regulation such as gene expression and appears to be necessary for the development of complex organisms. The ENCODE results were not necessarily unexpected since increases in attributions of functionality were foreshadowed by previous decades of research.
Additionally, others have noted that the ENCODE project from the very beginning had a scope that was based on seeking biomedically relevant functional elements in the genome not evolutionary functional elements, which are not necessarily the same thing since evolutionary selection is neither sufficient nor necessary to establish a function. It is a very useful proxy to relevant functions, but an imperfect one and not the only one.
SCience is never a "there thats it , we are done" Initial publications ere based upon specific efinitions and Im amazed that the "pseudogenes" were functional by the study"s own definition. Yet they readily stipulate to the "evolutionarily constrained" genes had to be "shut off" by some means because weve long known (as a parallel activity) the very function that a whole boatload of genes maintain.
Read up about how vitamin C is no longer mwtabolically produced by bats , primates, and guinea pigs.
Im anticipting the entire outgrowth of this study and the interspcies ones. Jut like the "Dinosur soft tissue" discovery mwrely gqve us a new method of fossiliztion, the ENCODE legacy will probably help to define the word "functional"