[Paleopsych] BH: Deleting Junk DNA Does No Harm

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Thu Oct 21 20:30:11 UTC 2004

Deleting Junk DNA Does No Harm

Mouse experiment reinforces theory that large chunks of the human genome
serve no function

    By Liz Brown
    Betterhumans Staff
    10/20/2004 3:38 PM

    Process of elimination: Deleting large chunks of DNA in mice does them
    no harm, supporting the theory that the human genome contains lots of
    useless junk

    Large segments of our DNA may have absolutely no function and could
    apparently be removed without ill effect.

    At least, this is what researchers from the [1]US Department of Energy
    Joint Genome Institute (JGI) and [2]Lawrence Berkeley National
    Laboratory in Berkeley, California discovered when they deleted large
    parts of [3]DNA sequences shared by mice and humans in lab mice.

    The researchers set out to discover what function--if any--noncoding
    DNA had. When the human DNA sequence was mapped, scientists found that
    98% of the [4]genome appeared to contain no genes.

    "In these studies, we were looking particularly for sequences that
    might not be essential," says [5]Eddy Rubin, director of the JGI. "We
    were surprised, given the magnitude of that information being deleted
    from the genome, by the complete lack of impact noted."

    Removing the walls

    The researchers began eliminating sections of mouse DNA to determine
    if the noncoding sections had any function. "To use an architectural
    analogy, we asked which walls in the room actually support the ceiling
    above," says Marcelo Nbrega, lead author of the study. "Remove the
    walls and you will know."

    Genetically engineering embryonic cells and then creating mice from
    these cells, the researchers deleted 2.3 million letters of DNA code
    from the 2.7 billion-base-pair mouse genome.

    When the researchers compared the genetically altered mice with normal
    mice, they could detect no differences in any areas, including
    viability, growth and longevity.

    "By and large, these deletions were tolerated and didn't result in any
    noticeable changes," says Nbrega. "An important caveat, however, is
    that no matter how detailed our analyses, our ability to test for a
    particular characteristic in mice is limited. All we know is that, in
    the time frame examined, there were no detectable changes in the
    specific features that we studied."

    The mouse genome is about 14% smaller than the human genome, but is
    surprisingly similar in its sequence. This means it is likely that
    eliminating these same areas in human DNA wouldn't have an effect on
    the human body, a finding that provides a better understanding of our
    genetic makeup.

    The research is reported in the journal [6]Nature ([7]read abstract).


    1. http://www.jgi.doe.gov/
    2. http://www.lbl.gov/
    3. http://www.wikipedia.org/wiki/DNA
    4. http://www.wikipedia.org/wiki/Genome
    5. http://www-gsd.lbl.gov/rubin/
    6. http://www.nature.com/nature/
    7. http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v431/n7011/abs/nature03022_fs.html

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