Re: Energy cost of copying junk DNA
- From: "wade" <wade.hines@xxxxxxx>
- Date: 16 Sep 2005 11:28:20 -0700
Friar Broccoli wrote:
> Hi All;
>
> If I understand correctly, about 95% of the human genome is
> junk. That means that every time a cell divides it replicates
> about 20 times as much DNA as it needs.
>
> So I have the following questions:
>
> 1) What percentage of total daily energy is spent on cell
> division (intestine, skin etc)? (Is energy consumption the
> best measure of resource use for this?)
>
> 2) How much extra energy/resources are used replicating
> with this junk than without it?
>
> Just to make these questions appear to be on topic, I will
> ask if any IDers can explain why the designer left so much
> junk in his/her/its creation?
One can provide some crude calculations that wind up suggesting
that 1% of a human cell's mass is DNA. With equally rough and
ready machinations you can say that DNA isn't much more expensive
to make and keep than other cellular macromolecules. So the
expense to carry the junk DNA is about 1% of the cost of a cell
building up it's mass. Lots more energy is spent in maintaining
homeostatis so the answer is "significantly less than 1%" of a
cells energy is spent maintaining junk DNA. My guess is at least
a factor of 20 less than 1%.
It does get more complicated when you consider the cost in
remodeling chromatin, methylating and demethylating DNA,
methylating, acetylating and otherwise modifying histones,
making enough proteins to repair and maintain extra DNA,
navigate through DNA and myriad additional housekeeping tasks.
(big houses take longer to clean than small cottages)
But similar housekeeping tasks are continually recycling
proteins, recycling RNA transcripts, adjusting osmotic
concentration and the whole cellular import/export labor
union.
So from a "back of the envelope" first shot, I don't see
that junk DNA is a significant expense. At least nothing to
justify hiring an accountant to track.
.
- References:
- Energy cost of copying junk DNA
- From: Friar Broccoli
- Energy cost of copying junk DNA
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