5 ms·

More than 90% of Human DNA Is Useless 'Junk,' Study Finds

3 points by chasef 12y ago

s_q_b 12y ago
This cuts against everything I've heard about genetics and epigenetic developments since the the complete of the HGP. It was my understanding that we were finding that the so-called "junk" DNA actually serves a variety of functions in regulating and controlling protein production and usage. Wikipedia seems to agree: "The Encyclopedia of DNA Elements (ENCODE) project[3] suggested in September 2012 that over 80% of DNA in the human genome "serves some purpose, biochemically speaking".[4] This conclusion however is strongly criticized by other scientists,[5][6] with a recent article claiming that "8.2% of the human genome is likely to be functional, while only 2.2% has maintained constraint in both human and mouse since these species diverged".[7]" https://en.wikipedia.org/wiki/Noncoding_DNA https://en.wikipedia.org/wiki/Noncoding_DNA
- dekhn 12y ago
  I'm still waiting for somebody to make a minimal human genome that removes all the Alu sequences and shows it's viable.
  - s_q_b 12y ago
    Or really a minimal version of any genome. Build me a fruit fly with the "non-coding" sequences removed, and show me that its phenotypically normal. The genomes are remarkably similar, thus proving the point while not involving potential ethical issues.
    - dekhn 12y ago
      Note, that I don't think this would be an easy experiment. For example, if you removed all the Alus, you would likely break something critically functional, but not be able to conclude specifically that it was due to removing the Alu, rather than, say, some other complicated genomic effect. Another way to look at it: pick a model organism (maybe c elegans), run many experiments in parallel, finding regions which can be removed and allow viability under a wide range of inducible environments (if you remove the heat shock proteins, but never put the worms in a hot environment, you might conclude you increased fitness). Find the largest regions you can remove independently, then start with pairs of regions (you can imagine that removing region 1 and region 2 independently would have no effect, but be fatal if combined), etc. The resulting genomes would probably still contain regions that contained no recognizable function, have no strong selection pressure, and yet still be completely necessary for viability. This is just speculation on my part, though.
- maxerickson 12y ago
  If only 2% of the human genome is coding proteins and if more than 90% of it is doing nothing, you still have room for ~7% of the genome to be functional, non-coding DNA.
seanflyon 12y ago
Over 90% of the human genome is able to mutate and still be viable. Much better than the reasoning I was expecting (We don't know what it does therefore it is junk), but still seems like a bit of a stretch.

3 points by chasef 12y ago

s_q_b 12y ago

This cuts against everything I've heard about genetics and epigenetic developments since the the complete of the HGP. It was my understanding that we were finding that the so-called "junk" DNA actually serves a variety of functions in regulating and controlling protein production and usage. Wikipedia seems to agree: "The Encyclopedia of DNA Elements (ENCODE) project[3] suggested in September 2012 that over 80% of DNA in the human genome "serves some purpose, biochemically speaking".[4] This conclusion however is strongly criticized by other scientists,[5][6] with a recent article claiming that "8.2% of the human genome is likely to be functional, while only 2.2% has maintained constraint in both human and mouse since these species diverged".[7]" https://en.wikipedia.org/wiki/Noncoding_DNA https://en.wikipedia.org/wiki/Noncoding_DNA

dekhn 12y ago
I'm still waiting for somebody to make a minimal human genome that removes all the Alu sequences and shows it's viable.
- s_q_b 12y ago
  Or really a minimal version of any genome. Build me a fruit fly with the "non-coding" sequences removed, and show me that its phenotypically normal. The genomes are remarkably similar, thus proving the point while not involving potential ethical issues.
  - dekhn 12y ago
    Note, that I don't think this would be an easy experiment. For example, if you removed all the Alus, you would likely break something critically functional, but not be able to conclude specifically that it was due to removing the Alu, rather than, say, some other complicated genomic effect. Another way to look at it: pick a model organism (maybe c elegans), run many experiments in parallel, finding regions which can be removed and allow viability under a wide range of inducible environments (if you remove the heat shock proteins, but never put the worms in a hot environment, you might conclude you increased fitness). Find the largest regions you can remove independently, then start with pairs of regions (you can imagine that removing region 1 and region 2 independently would have no effect, but be fatal if combined), etc. The resulting genomes would probably still contain regions that contained no recognizable function, have no strong selection pressure, and yet still be completely necessary for viability. This is just speculation on my part, though.
maxerickson 12y ago
If only 2% of the human genome is coding proteins and if more than 90% of it is doing nothing, you still have room for ~7% of the genome to be functional, non-coding DNA.

seanflyon 12y ago

Over 90% of the human genome is able to mutate and still be viable. Much better than the reasoning I was expecting (We don't know what it does therefore it is junk), but still seems like a bit of a stretch.