Oolon Colluphid

Yeah, but...

Really? I bow to your much greater knowledge of course, but perhaps you could explain that one further, because it’s the opposite of what I have read.

So that conclusion depends on your reply to my query above .

Erm, Peez, I’m sure you’re aware, however, that mitochondria used to be separate organisms. See <a href="http://www.nature.com/genomics/papers/r_prowazekii.html" target="_blank">here</a>, though I’m sure you must already have.

So it’s not a semantic distinction, but one of time, or perhaps degree of symbiosis. (Pushed to an extreme, one could, as Dawkins might encourage us to do as a thought experiment, view each gene as in symbiosis with all the others in a genome .) In other words, I’m unclear as to why the distinction is a valid one, or rather, maybe it is a quantitative distinction, not a qualitative one?

In confusion and in need of another dip into Brock’s, Oolon

Oolon Colluphid

He goes further, and considers all the other genes in a genome to be themselves part of the environment each gene ‘lives’ in. Thus the environment that suits a gene for sharp teeth is not just one containing prey animals, hiding places, but also ‘genes for’ meat digestion, hunting strategies, camoflage, and so on. (Note though that he views this as a useful and illuminating thought experiment, not a reducionist that’s-all-there-is-to-it argument .)

Oolon

Peez

No, I would argue no such thing, and I cannot imagine how you came to that conclusion. I do not consider mitochondria parasites, nor even separate organisms. In this sense, they are fundamentally different from the other examples (including wolbachia). But this still misses the point. EVEN IF we accept that mitochondria and wolbachia are not fundamentally different, and EVEN IF we accept that they are both "inherited", the inheritance is still through DNA (as far as I can see). You did post: If wolbachia is not an example of non-nucleotide inheritance, I am not sure what its relevance is here. Isn't this like saying that human traits are all "inherited" by the transmission of eggs and sperm and not their DNA? This whole discussion erupted from a difference of opinion on how to define evolution. The argument (as I understand it) was made that evolution can include changes that are not changes in allele frequency. Wolbachia has been presented as an example of "non-nucleotide inheritance" in this context. I have yet to see any explanation as to how wolbachia represents an example of evolution without change in allele frequencies. Fair enough (and I do thank you, they are interesting articles), but it is notable that the article talks about the effects of wolbachia infection on evolution, rather than wolbachia infection as evolution. Thank-you, I did miss any earlier reference to this. It is exactly what I have been asking for, an example of non-nucleotide inheritance. Granted, we could quibble over the definition of "environment" (Dawkins probably would, with his "selfish gene" approach), but I would accept this as an example of non-nucleotide inheritance. It is fascinating. It is also highly exceptional. The article states: Thus, I am not ready to dump the standard definition of evolution just yet. The ciliate example suggests that we have to be prepared to be flexible. The standard definition of evolution assumes that genetic information is passed only through alleles. Perhaps being more general and defining evolution as a change in the frequency of specific genetic information would do the trick, but given that at least 99.999% of such information is found in nucleotides, the old definition seems practical. Certainly dismissing it seems excessive.

You posted earlier: and Since only one example of non-nucleotide inheritance (restricted to a particular group) seems to be known, I cannot agree with those statements.

Meanwhile, pz has posted: and So I would like to ask for a few examples from this book "full of ‘em", now that we are (hopefully) clear on what non-nucleotide inheritance is. I also hope that I have demonstrated that I am willing to accept non-nucleotide inheritance if I see it. Please show me if it is more common that the article mentioned states.

Peez

Peez

I am not sure exactly what you mean here, but I subscribe to Dougla J. Futuyma's definition, in Evolutionary Biology, Third Edition: Peez

pz

I would be happy to do so, but I'm afraid I'm steering clear of this thread since my point of view seems to rather seriously antagonize some people.

Have you read Lawrence's _Making of a Fly_? It's all about genes, of course, but it is also readily apparent that genes are insufficient, and that maternal and epigenetic factors are just as important. More directly, you might try looking at Lewontin's _Triple Helix_, or Oyama's _Ontogeny of Information_ or _Evolution's Eye_. This is a subject near and dear to me, but I'd rather not aggravate people who otherwise have respected and valuable opinions.

Since you asked, I'll mention one specific example: activation and distribution of signalling proteins in the D/V specification system of Drosophila. It's very intricate and is dependent on higher-level organization of maternal tissues.

[ November 01, 2002: Message edited by: pz ]</p>

Peez

Sorry, I am being a bit sloppy. I meant that mitochondria do not have a ‘complete' genome: they certainly have some DNA, but some genes that code for proteins that are critical for mitochondrial function are found in the nucleus. Thus, in a sense, their "genome" is partly in the matrix of the mitochondria and partly in the nucleus. I apologize for the confusion. In part . Yup.

Quote:

So it's not a semantic distinction, but one of time, or perhaps degree of symbiosis. (Pushed to an extreme, one could, as Dawkins might encourage us to do as a thought experiment, view each gene as in symbiosis with all the others in a genome .) In other words, I'm unclear as to why the distinction is a valid one, or rather, maybe it is a quantitative distinction, not a qualitative one?

Not so much a question of time, but of evolution . The "infection" of early eukaryotic cells by proto-mitochondria was not evolution. There was no change in allele frequency anywhere. From that close association between proto-mitochondria and the "host" eukaryotic cell, there have been changes in allele frequency in both the eukaryotic cell and it's "guests". The line between there being two organisms and there being one with mitochondria is obviously fuzzy, but I consider them to have been fused before the present. In any event, the evolution of mitochondria is what happened after "infection". This is an interesting topic which helps to focus just what evolution is.

Peez

[ November 01, 2002: Message edited by: Peez ]</p>

Peez

Good points.

Peez

Peez

With respect, I don't believe that it is the point of view that has antagonized some people. Intentionally or unintentionally some of your posts have come across as rather abrasive in tone. I have made an effort to give you the benefit of the doubt, and I hope you will afford me the same, but I feel that I must point out that your point of view was (at the very least) not the only issue. Important to what? Ontogeny is not evolution, and I have repeatedly stated that the environment influences phenotype. Unfortunately, I am not familiar with these books and cannot comment further at this time, but I thank you for the references. It is certainly not worth building antagonism between members here. I don't know anything about this, could you provide a reference? Thanks.

Peez

pz

Oh, right. I really have to stop insulting people by comparing them to Behe and Vanderzyden. That was me doing that, right?

It is getting rather exasperating to be accused of being condescending when I try to explain my position, a position that very few people here seem to comprehend, and one that apparently very few people here have studied at all, given the number of times I've mentioned basic texts on the topic and am told that they are unfamiliar. My apologies if the fact that I know something that others do not is interpreted as being abrasive.

See the Lawrence text, or any developmental biology textbook. or for a recent review,
Stathopoulos A, Levine M. (2002) Dorsal gradient networks in the Drosophila embryo. Dev Biol 246(1):57-67

Simpler example: vertebrate eggs have to be primed with beta-catenin. beta-catenin can't be assumed to be automatically expressed in every cell. It has to be explicitly activated by epigenetic interactions. This pattern is inherited. It is also not determined by the genome.

RufusAtticus

*Bump*

Peez and DD, I'll have a post for y'all monday or tuesday.