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Earth Science

Carnivorous Plant Ejects Junk DNA 116

sciencehabit writes "The carnivorous humped bladderwort, found on all continents except Antarctica, is a model of ruthless genetic efficiency. Only 3% of this aquatic plant's DNA is not part of a known gene, new research shows. In contrast, only 2% of human DNA is part of a gene. The bladderwort, named for its water-filled bladders that suck in unsuspecting prey, is a relative of the tomato. The finding overturns the notion that this repetitive, non-coding DNA, popularly called 'junk' DNA, is necessary for life."
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Carnivorous Plant Ejects Junk DNA

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  • junk dna (Score:5, Interesting)

    by bdabautcb ( 1040566 ) <bodaciouswaggler@y a h o> on Monday May 13, 2013 @02:09PM (#43712525)
    My understanding is that junk DNA is no longer a useful term because the DNA that isn't translated has been found to have structural and other epigenetic properties. I wonder if the complexity of mamallian vs. plant development plays a role here. Any biologists out there?
  • by Cyberax ( 705495 ) on Monday May 13, 2013 @02:15PM (#43712595)
    Wrong! Most of junk DNA is... wait for it... JUNK!

    We can tell the composition of the junk for approximately 66% of the human genome. There is a small amount of regulatory elements mixed with all this junk, but the junk itself is not necessary for anything.

    Even without the extreme examples such as bladderwort we readily observe 10x variability in the amount of DNA between fairly recently separated species.
  • Re:junk dna (Score:5, Interesting)

    by Hatta ( 162192 ) on Monday May 13, 2013 @02:28PM (#43712741) Journal

    Not all untranslated DNA has other properties. Some of it really does just exist because it's good at getting itself replicated. It's an open question how much non-coding DNA exerts regulatory effects and how much is actually junk. This paper indicates that in at least one eukaryote, 3% non-coding DNA is sufficient to regulate all the coding DNA.

    If that holds in mammals (unlikely, but not out of the question), the vast majority of our non-coding DNA would still be "junk". Human DNA is 98% non-coding, or 2% coding. 3% of 2% is a rounding error here, so it would still be accurate to say the human genome is 98% "junk". If regulatory sequences outnumbered coding sequences 10:1 you're still looking at >75% of the human genome being "junk".

    I don't think the concept of "junk" DNA is ever going to go away. Evolution would predict that sequences that are good at replicating themselves would accumulate in the genome, even if they don't do anything "useful". And random errors that accrue during copying will persist unless there's a mechanism to select against them. If we found that 100% of our DNA had a purpose, that would be a pretty strong argument against the theory of evolution.

    The interesting question here is what selective forces drive this plant to excise unnecessary DNA, and what mechanism it uses to do this. Understanding that mechanism might lead to future gene therapies.

  • by WillAffleckUW ( 858324 ) on Monday May 13, 2013 @04:07PM (#43713651) Homepage Journal

    I beg to differ with the "conclusion" that most DNA is "junk" DNA.

    As we learn how DNA is used to create RNA, mRNA, siRNA, miRNA, circRNA, microRNA, etc - by folding, spindling, adapting to environmental messages and signals, we find that a lot of what you think is "junk" DNA is in fact ... NOT.

    Some is, of course, but the conclusion is ... WRONG. Most of the actual junk is actually viral rewrites (true junk), but a lot of the other stuff is boostrap shifted code designed to handle various conditions that may or may not be present.

    For example, if you take a drug that shuts down a primary biochemical pathway, the cells turn on a second biochemical pathway - which may or may not be optimized. If the secondary biochemical pathway is shut down by drugs or damage, a tertiary - conserved, usually evolutionarily conserved fallback from when you were a fish or ratlike creature - kicks in.

    You think it's junk. It's just code that turns on when you mess with the program or force certain conditions to occur.

"my terminal is a lethal teaspoon." -- Patricia O Tuama