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    And the junk DNA train rolls on...
    By T. Ryan Gregory | August 15th 2008 07:40 AM | 1 comment | Print | E-mail | Track Comments
    About T. Ryan

    I am an evolutionary biologist specializing in genome size evolution at the University of Guelph in Guelph, Ontario, Canada. Be sure to visit

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    This appeared in my weekly automated journal search. I have ordered the paper as I can't find an online copy, but the abstract pretty much covers what the argument will be. Same old pre-1980s adaptationist idea presented as radically novel.
    Mallik, M. and Lakhotia, S.C. 2008. Noncoding DNA is not "junk" but a necessity for origin and evolution of biological complexity. Proceedings of the Indian National Science Academy Section B - Biological Sciences 77 (Sp. Iss.): 43-50. All eukaryotic genomes contain, besides the coding information for amino acids in different proteins, a significant amount of noncoding sequences, which may or may not be transcribed. In general, the more evolved or biologically complex the organisms are, greater is the proportion of the noncoding component in their genomes. The popularity and success of "central dogma of molecular biology" during the last quarter of the 20(th) century relegated the noncoding DNA sequences to a mortifying status of "junk" or "selfish", even though during the pre-"molecular biology" days there were good indications that such regions of the genome may function in as yet unknown ways. A resurgence of studies on the noncoding sequences in various genomes during the past several years makes it clear that the complex biological organization demands much more than a rich proteome. Although the more popularly known noncoding RNAs are the small microRNAs and other similar species, other types of larger noncoding RNAs with critical functions in regulating gene activity at various levels are being increasingly,identified and characterized. Many noncoding RNAs are involved in epigenctic modifications, including imprinting of genes. A comprehensive understanding of the significance of noncoding DNA sequences in eukaryotic genomes is essential for understanding the origin and sustenance of complex biological organization of multicellular organisms.
    See also: Junk DNA and the Onion Test.

    Comments

    Gerhard Adam
    From a recent news item entitled "Bacteria Can Be Infected By Viruses"

    In an ingenious fashion, the bacteria build pieces of viral DNA into their own DNA. The 'adopted' segment of DNA works like a snapshot in a photo album, a type of memory that reminds the bacteria during a subsequent encounter with the same virus. At that point, the viral DNA is recognised, after which the bacteria set a system into operation that ultimately leads to the breakdown of the virus.

    The researchers determined that one of the proteins cuts the 'virus snapshot' out of the photo album, and together with the other five proteins, compares the snapshot with the DNA of the invading virus. In the same way, other viruses in the photo album can also be rendered harmless.

    This strengthens my belief that much of the non-coding DNA is actually a "database" of sorts which is used in such functions as immune system recognition of invaders. I realize that understanding how such "knowledge" would be conveyed back to the DNA so that it could be passed on to future generations is problematic, but nevertheless, the bacteria presents a similar problem. Clearly, we're dealing with post-reproductive DNA modification which can be used for future events based on past experience. In other words, regardless of whether the infected bacteria die, the information from the encounter has been added to the existing DNA and is available to futue generations. This implies a feedback mechanism which suggests that somehow some environmental data is available for transmission into future generations.
    Mundus vult decipi