How is it an amoeba can have 200 times the DNA a human has ?

[CharonY]

And it is unlikely that a general answer can be given as the reasons for each group to accumulate DNA may be very different, depending on their history. In some cases the presence or absence of certain selective pressures (or combination thereof) may be part of the explanation. Also genomic parasitism is an interesting element here (especially for non-coding elements). Likewise more mechanistic approaches including considering cell size and metabolic activities have been proposed. As already mentioned, this is still under investigation.

However, from my little corner of academia it seems to me the overall interest seems rather limited. Mostly because the elucidation of mechanisms of genome evolution are probably more interesting than trying to get an overarching explanation (which possibly does not exist) to explain a (for some) contra-intuitive phenomenon.

[dr.syntax]

I would like to point out that a lot of the complexity in us animals actually exists in the nervous system, rather than having a genetic basis. For example, the genetic information of a human fits on a CD. But how much information is stored in the nervous system? I would wager we have amoebas beat in that sense. At the cellular level, though, human cells are not at all impressive.

 

REPLY: Yes, as far as DNA we humans don`t seem very impressive. We are slightly ahead of dogs but certain frogs have about 3 times as much. And of course there is the mighty Amoeba dubia ranking somewhat more than 200 times as much. There are different amoebas and we don`t do do quite so badly compared to them. Strangely if it`s true the Easter Lilys and puffer fish rank up there with the mighty Amoeba dubia. So there doesn`t seem to be much rhyme or reason to it. I`ve spent some time looking into it. Much has been written about this C-value enigma or paradox. A lot of it just confuses me. As far as I know it is still a bit of an enigma to most of the people who have looked into it. There may be someone out there who finally put it all together, I don`t know. Take Care, Dr.Syntax

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First of all, if you're looking for the C-value of several organisms, there are entire databases devoted to this;

 

Animals: http://www.genomesize.com/

 

Plants: http://data.kew.org/cvalues/homepage.html

 

...

 

The term "C-value paradox" is quite misleading, "C-value enigma" makes more sense. It's not a paradox in the sense that we very well know what mechanisms could generate such pattern. It was a paradox only until we discovered that so much DNA is noncoding, "junk". In short, again, if the concept of C-value and junk DNA are so difficult to understand for some people, it's because they are either convinced natural selection is the main driving force of evolution, or, even worst, they think it's the only one.

 

Now, the C-value enigma is not to be solved with a simple answer, there are too many things going on inside the genome; some groups have more transposable elements than others, some groups are more likely to experience whole-genome duplication, some selective pressure seem to keep the genome small in some group with high energy demands (like: flying organisms) and genome size also has an impact on the phenotype (cell size, development rates...), so negative selection is certainly not out of the picture...

 

You're certainly not going to get any good answer to your question here, the various solutions to the C-value enigma are currently actively debated, you would likely not even get the same answer from two scientists working on the subject. Still, if you want to study the question further, I suggest Gregory's "onion test" (http://www.scientificblogging.com/genomicron/junk_dna_and_the_onion_test), it's a nice, well-written article, and "the evolution of the genome" (a book edited by Gregory). He's specialized in the genome size debate, and he's also a skilled science popularizer.

 

REPLY: The information you gave me will keep me busy for some time. I will print any data bases as to gene counts. I`ve begun collecting them. You`ve been extremely helpful to me and I appreciate it.Also, I have adapted your" C-value enigma" wording because I agree with you. I noticed your Poincare quote. I too am an admirer of Henri Poincare Regards, ...Dr.Syntax

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I hit the mother lode of data bases thanks to you. This beyond what I had ever hoped for. Thank you so very much.They are big and I put them on favorites for now. I need to get some more ink if I intend to print them up. ...Dr.Syntax

[iNow]

REPLY: The information you gave me will keep me busy for some time. I will print any data bases as to gene counts.

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They are big and I put them on favorites for now. I need to get some more ink if I intend to print them up. ...Dr.Syntax

 

Tree killer.

[dr.syntax]

Tree killer.

 

Reply: Data bases far to large and complexly organized to print I think. Anyway I guess you don`t use a printer to save trees, or do you when you feel like it ? ...WHATEVER, ...Dr.Syntax

[mooeypoo]

Reply: Data bases far to large and complexly organized to print I think. Anyway I guess you don`t use a printer to save trees, or do you when you feel like it ? ...WHATEVER, ...Dr.Syntax

I think that was a joke, dr.syntax

[iNow]

Reply: Data bases far to large and complexly organized to print I think. Anyway I guess you don`t use a printer to save trees, or do you when you feel like it ? ...WHATEVER, ...Dr.Syntax

 

Mooeypoo is correct, Dr.Syntax. It was a joke. I'm sorry if I have offended you, as that was not my intent. Also, FWIW... I haven't printed anything myself in over 2 years, and even then it was just a map to a party. I manage all of my data electronically. I find it easier to sort, store, and categorize that way, especially since I tend to work with such large databases. Besides, papers always wind up in a great big mess with me, plus... I try to do my part to be pro-environment and not waste when not necessary.

 

Either way, that's all off-topic. Please accept my apologies.

 

 

 

As per the thread topic, it seems to have been answered AFAICT. Do you agree?

[dr.syntax]

Mooeypoo is correct, Dr.Syntax. It was a joke. I'm sorry if I have offended you, as that was not my intent. Also, FWIW... I haven't printed anything myself in over 2 years, and even then it was just a map to a party. I manage all of my data electronically. I find it easier to sort, store, and categorize that way, especially since I tend to work with such large databases. Besides, papers always wind up in a great big mess with me, plus... I try to do my part to be pro-environment and not waste when not necessary.

 

Either way, that's all off-topic. Please accept my apologies.

 

 

 

As per the thread topic, it seems to have been answered AFAICT. Do you agree?

 

I accept your apology and said I was sorry for the misunderstanding. I do not know what AFAICT means. I certainly never complained about anything to any moderator ever unless replying in the public forum to a posting by a moderator. I never event knew about the alert button until mooey pooey explained it to me yesterday. I have never once used it. Is that what AFAICT is about. Mooey Pooey watches my postings on her own. I don`t appreciate the close scrutiny I`ve been getting. Let us both try put the past behind us and I will try very hard not to offend you. We have to get along in this forum together or not. I would prefer to try to get along. We actually do agree with each other on many important isssues. ...Dr.Syntax

[iNow]

AFAICT = As far as I can tell.

[dr.syntax]

AFAICT = As far as I can tell.

 

REPLY: As far as I can tell it has not been answered with any certainty although many have tried.I am speaking of the academic World per se. And I certainly see no compelling arguments here in this forum. The more you look into the C-value enigma the more complex it becomes. It`s a topic many of the best in the field have looked into. They have come up with some partial answers that seem to make sense to a point. I recall one saying his argument worked up to the point, but fails at that point of explaining the massive C-value for the amoeba dubia. There are about as many varying opinions out there about all this as there are scientists taking a serious look into it. you take care, ...Dr.Syntax

Edited September 29, 2009 by dr.syntax

[iNow]

Well, I've seen many different answers to the question in your thread title, answers which were very certain and also very accurate. Is it possible that it's just that none of them are the answer you want?

[dr.syntax]

Well, I've seen many different answers to the question in your thread title, answers which were very certain and also very accurate. Is it possible that it's just that none of them are the answer you want?

 

REPLY: I have no idea of what you are talking about. I read post #25 by PhDP. He surely sees no very certain answers to this question and doesn`s expect I`ll find any. I`ve been blogging this a good part of today and there is no consensus I can see. A short article by T.Ryan Gregory is one such article at : http://www.scientificblogging.com/genomicron/junk_dna_and_the_onion_test . I see we find and interpret things quite differently. For you to think that anything posted in this thread had convinced me that this C-value enigma had been resolved or solved is the exact opposite of what I see here. Have a nice day. ...DS

Edited September 29, 2009 by dr.syntax
spelling

[Mr Skeptic]

That's at least superficially true. But then, where does the complexity of the nervous system come from? It's a pattern emerging from the "rules" dictated by the genome. So in a sense the complexity is already there, just in "compressed format."

 

Not so, you do not for example have the information for the English language coded into your genome in some compressed format. There isn't even enough information in the genome to store all that information no matter how compressed. What you are talking about is emergent behavior. The zygote sets up a simple nervous system and rules for it to follow, and from there it's all sensory input and feedback loops. A complex pattern emerges from simpler behavior of individual neurons.

 

I've always liked emergent behavior. Complex simplicity

 

While in a single-celled organism, I guess everything is expressed all the time, and the genome has to do things that in a multi-celled organism would be done by emergent macrostructures?

 

Yeah, that's what I was getting at. Our multicellular nature enables us to minimize lots of the problems cells face, so that the organism as a whole helps maintain some aspects of homeostasis on behalf of the cells. I suppose this could be considered another example of emergent behavior.