Re: Gene duplication rate

Lorentz wrote:
On Aug 13, 1:20 pm, dkomo <dkomo...@xxxxxxxxxxx> wrote:


Duplications result from a phenomenon known as "unequal cross-over"
which occurs during meiosis of eukaryotic cells. This is a chance event
which happens when two homologous chromosomes misalign before they cross
over, resulting in one chromosome getting a redundant stretch of DNA.

And the other chromosome getting a reduced stretch of DNA. If you
include gene duplications, then you have to include gene deletions. A
gene deletion has about the same chances of being advantageous or
disadvantageous as a gene duplication. If the rates are roughly equal,
then the average genome size won't change.

I don't agree here. I think a gene deletion is far more likely to lead
to a dysfunctional organism than a gene duplication. Having an extra
gene probably doesn't have much effect if the regulation of that gene is
still intact. Then that extra gene is free to mutate and possibly lead
to a useful new function.

Of course, the deleted gene doesn't have the opportunity to mutate
further down the road. Maybe one of the reasons that C. elegans has a
small genome is that in its lineage, there were as many deletions as
duplications. Further, it remained a simple organism because there
weren't as many genes to mutate. That and the fact that it does very
well in its niche as it is.


--dkomo@xxxxxxxx


.

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