[dmach]

First heard of this from Frank Ryans book Virolution. It explains a lot of what had been termed junk DNA previously.

[otakucode]

I've not heard of that book before but will have to check it out. Did it happen to mention any of the experimental research done showing that removal of 'junk DNA' makes organisms (microorganisms anyway) less capable of adapting to environmental change? As I remember it, some researchers took a bacteria (probably e. coli, that's usually the easiest to do this sort of thing with but I'm not certain) and separated out two populations. In one they let it be, and in the other they stripped out all 'junk' DNA that didn't play a role in protein synthesis. Then they introduced harsh conditions to both (I think something like high acidity or low availability of food or something like that) and while the 'junky' population adapted relatively quickly, the 'pure' population quickly died off and wasn't able to gain beneficial mutations quickly enough to survive.

[21]

And there is another line of thought.

Bacteria's pay dearly for each extra bit of DNA they carry, since the energy cost of DNA replication is linear with respect to the length.

Bacteria's with less DNA can replicate more quickly and thus outcompete other bacterias.

The fact that after so many generations they still carry that "junk" which they pay for suggests it really is useful in one way or another.

[dmach]

I'm not sure if junk DNA was covered directly in the book. It may of been a radio interview about the book where I heard junk DNA discussed. From what I remember a large portion of say our DNA was not understood so was considered junk but old viruses assimilated into our DNA could make up as much as 40% of us. The assimilated DNA could then act like a defence so removing it would be bad.

[dekhn]

No, most of the viral junk DNA is just repeating copies of non-coding regions (Alu and other repeats). This is an example of an actual coding gene from a virus, which is much more rare and sporadic.

[eighthnate]

Excellent book. It made the subject so readily accessible to the layman.

[dmach]

And yet it doesn't shy away from the details. One of the main things I took away was how symbiosis could be the driving force behind evolution instead of purely the traditional competitive based changes.