From: Alejandro Dubrovsky (email@example.com)
Date: Sun Feb 03 2002 - 13:55:08 MST
On Mon, 2002-02-04 at 06:38, firstname.lastname@example.org wrote:
> I did not know that, but come to think of it, it does make sense.
> Let's consider ourselves a little transcriptor machine, looking to read
> some DNA and make RNA from it. Here's some. Now, which strand is which?
> And which way is "forward"? The DNA extends for thousands of miles in
> each direction on our scale. It's twisted around itself so there is no
> way to distinguish one strand from a passive mirror. And one direction
> looks like the other. So there is no reason we can't read genes in
> either direction, and on either strand.
> The only reason I could see for evolution to prefer using a single
> strand and a single direction were if that created a more compact and/or
> efficient way of packing all the genes into the DNA. The real mystery
> to me is why efficiency is seemingly not a factor and why junk DNA is
> allowed to proliferate. But given that efficiency is not an issue,
> then in hindsight it is predictable that both directions and strands
> could be used.
That doesn't make sense to me. Genes can be read off both strands
because efficiency IS important. It is important in bacteria (the
shorter it is, the quicker it can reproduce) and in viri (which has to
pack it into a protein) which is exactly where you are more likely to
see the tricks of genes on both strands and multiple reading frames on
each (and where junk DNA is non-existant).
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