On Feb 19, 7:18=A0am, dsummers...@[EMAIL PROTECTED]
wrote:
> How is it possible for DNA to reproduce at the speeds it does? DNA
> bases find their place at a rate of up to 1000 base pairs per second
> at a replication site. I have a hard time picturing this. =A0Imagine a
> string encrusted with magnets, thrown into a bag of short magnetic
> clusters and shaken rapidly. I can imagine, if the design was clever
> enough, that occasionally a cluster would find its proper place at the
> end of the string, as the clusters got knocked around and one just
> happened to land at the right angle to get knocked into the right
> place to join at the end of the string. =A0But this would be a very slow
> process. Most of the time, the clusters would block each other by
> fitting in a not quite perfect way (a local energy minimum) rather
> than instantly finding a perfect fit (a global energy minimum). How
> does it happen so fast in the cell?
> If you watch visualization movies of the process, it looks like a time-
> reversed video, because it is so clearly going from a disordered state
> (base pairs floating nearby) to an ordered state (a DNA molecule) very
> quickly.
Think about the scale, and the distances involved. They are very, very
short.
As a result, you don't have to move things far, and a *lot* of
attempts can
take place in a very short time. In fact, you can argue that 1000bp/s
is
slow - if things were better arranged the process could be much
faster.
Compare with modern electronics, which operates a million times
faster,
on a similar scale.
It may look like a reverse entropy process to you, but iirc, the
energy is
coming from two of the phosphate groups being removed from
nucleotide triphosphates by hydrolysis.
Peter Trei
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