Comments on: The onion test.

By: Uncommon Descent | The original ‘onion test’ is a biological non-sequitur

Mon, 10 Oct 2011 18:16:40 +0000

[...] to ask? No. As Jonathan Wells writes, in The Myth of Junk DNA (pp. 85-86): The “onion test,” according to Gregory, “is a simply reality check for anyone who thinks they have come up with a universal [...]

By: P Garrison

P Garrison — Mon, 18 Jul 2011 18:54:31 +0000

What was removed was about 1.5 million bp if I remember correctly, which is about 0.05% of the genome, not 3%. 3% would be about 90 million bp.

By: Is so-called "junk" DNA really useless? - Quora

Is so-called "junk" DNA really useless? - Quora — Fri, 08 Apr 2011 10:36:41 +0000

[...] [...]

By: T. Ryan Gregory

T. Ryan Gregory — Wed, 16 Dec 2009 18:23:07 +0000

Ok, but if it doesn’t account for genome size, it is very uninteresting.

By: T. Ryan Gregory

T. Ryan Gregory — Wed, 16 Dec 2009 18:20:29 +0000

Thomas Wicker: There are actually much better examples that comparing Onions and people. Take the grass Brachypodium (a close relative of wheat). Wheat has a 20 times larger genome than Brachypodium. Both are grasses, both look very similar, both are happily growing.

Actually, wheat is a poor choice because it is polyploid. Note that I wrote the following in the post:

Further, if you think perhaps onions are somehow special, consider that members of the genus Allium range in genome size from 7 pg to 31.5 pg. So why can A. altyncolicum make do with one fifth as much regulation, structural maintenance, protection against mutagens, or [insert preferred universal function] as A. ursinum

By: Thomas Wicker

Thomas Wicker — Wed, 16 Dec 2009 08:26:21 +0000

There are actually much better examples that comparing Onions and people. Take the grass Brachypodium (a close relative of wheat). Wheat has a 20 times larger genome than Brachypodium. Both are grasses, both look very similar, both are happily growing. The Junks seems to have no effect.

By: Keith Grimaldi

Keith Grimaldi — Wed, 16 Dec 2009 07:43:15 +0000

I don’t think that either “no-function” or “protective” hypotheses need to explain vastly differing genome sizes. Neither propose that genome size evolved to fit specific needs, rather, the protective hypothesis would propose that the repair mechanisms evolved to the necessary fidelity required to cope with whatever circumstances existed (including the amount of non-coding DNA). Both no-function and protective accept that the non-coding DNA happened by chance and was allowed to build up because there is not strong reason to get rid of it, since it is not such an energy consuming resource to replicate it etc (except maybe for high metabolic rates where some needs to be discarded?). regarding genome size and life-span the only proviso for a protective property is that there would need to be sufficient non-coding DNA to support a life-span long enough to reproduce. This does not predict though that genome size is tightly linked to lifespan – for protection, a genome with a majority of non-coding DNA would be necessary but not sufficient for an adequate life-span, but this is not at all incompatible with widely varying genome sizes, including enormous genomes in short lived organisms.

I think that a key is in the definitions of purpose. If it is proposed that the non-coding DNA evolved to fulfil a universal function then I think it fails the onion test. If it is proposed that other mechanisms such as DNA repair apparatus evolved to the necessary complexity then this is not proposing a universal “role” for non-coding DNA, it assigns a useful property to non-coding DNA but does not I think fail the onion test

By: eddie

eddie — Sun, 18 Oct 2009 04:06:49 +0000

Sorry, Anonymous and Intelligent Designer. Your propose solution fails the second part of the Onion Test; why do some species of onion need vastly more DNA than others.
In particular, the bit about dealing with more varying environmental stresses: It’s the different environments that lead to the speciation.
Again, evolution fits the facts and design does not.
Also, re Esko Heimonen: A bigger genome wouldneed a bigger nucleus, at least in those cells that have them. But the nucleus is a small size compared to the whole cell.

By: Intelligent Designer

Intelligent Designer — Tue, 13 Oct 2009 05:05:32 +0000

Unlike humans, onions can't control their environment or move away from it. Onions have no choice but to adapt. It could be that onions were designed with a lot of adaptive capacitance allowing its descendents to morph into onions that could thrive in many different environments. Deletion of some "junk" DNA could then easily result in a viable onion, because it would be an onion with less adaptive capacitance than the original but still able to produce offspring that could thrive in the current environment. Multiple lines of deletion of DNA used for adaptive capacitance could also result in speciation and account for the various sizes for onion DNA.

Also, why would anyone think there is a universal function for “junk” DNA. Isn't it more probable that there are many functions performed by "junk DNA" waiting to be discovered and that it will take hundreds of years of tedious research to decipher it all?

By: Esko Heimonen

Esko Heimonen — Sat, 19 Sep 2009 07:49:33 +0000

Oi! Mr. blogger. 9/14 was a serious proposal. There never was a condition that the universal function could not be wasteful to the extreme. What was the prize again? :)