Re: Ultraconserved Elements in the Genome: Are They Indispensable?

Puppet_Sock wrote:

On Sep 4, 10:14 pm, "George" <geo...@xxxxxxxxxxxxxxx> wrote:

http://www.lbl.gov/Science-Articles/Archive/Genomics-ultraconserved.html

[snip]

Ok, this is me being straightforwardly ignorant of the topic.
Is there a web site that gives a good non-technical explanation
of what these "ultraconserved" sties are?

Simple enough to do it here. "Ultraconserved" just means "very
conserved". Here, it's being used to refer to small regions of the
genome that are identical between rats and humans, i.e. that have not
changed one little bit in somewhere between 60 and 80 million years.

And what standard
thought on "junk DNA" is?

Junk DNA is simply enough defined. It's DNA that has no function in the
organism. Now we just have to argue about what's junk and what isn't,
and how you tell. A few people (some creationists, for example) think
there's no such thing as junk DNA. Usually, junk can be detected because
it's not conserved, which means that it evolves at the rate of neutral
evolution, mutations just randomly drifting to extinction or fixation.
Natural selection prevents harmful mutations from reaching fixation, and
so generally makes the rate of molecular evolution slow down. So we can
detect non-junk DNA because it's conserved, i.e. evolving at less than
the neutral rate.

Ultraconserved sequences are clearly not junk, and that's clear simply
because they are so conserved. If they weren't preserved by selection,
they would become mutually unrecognizable in much shorter time than
separates humans from rats.

There are of course many caveats. Sometimes natural selection may speed
up the rate of evolution for a while, if the environment changes such
that the currently common sequence is now disadvantageous. And there are
some genes where novelty is useful in itself, as for example parasites
and hosts fight to recognize each other. In such cases functional
regions may evolve at *greater* than the neutral rate. But never mind
that for now.

I look at this article, and several
other referenced journal articles down thread, and my eyes
just glaze over. I be a physics type, not a biology type.

That's one thing us biology types are here for. Did that help? at all

.

Relevant Pages

  • Re: Junk DNA: A hypothesis
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  • Re: Junk DNA reveals vital role III
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  • Re: Junk DNA reveals vital role III
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  • Re: Junk DNA reveals vital role III
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