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Does The E. Coli Long-term Evolution Experiment Evolution


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#1 Starter

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Posted 18 March 2010 - 07:31 PM

The E. Coli long-term evolution experiment is an ongoing study led by Richard Lenski. The study tracks genetic changes in 12 initially nearly identical populations of asexual Escherichia coli bacteria. The experiment started on February 24, 1988 and on February 14, 2010 the populations reached the milestone of 50,000 generations.



QUESTIONS:
What implications does this study have on the (Darwinian) Theory of Evolution?

Evolution Supporters

a.) For those of you who are familiar with this study, is it possible that the adaptations in this study were simply the result of recessive or dormant genes that were already present?

b.) How do you prove empirically that an adaptation is *actually* an adaptation (creating new genetic information) and not a case of dormant or recessive genes?


Evolution Opposers

a.) There is a New Theory of Evolution. Is it possible for this "new" theory to be both accurate and in line with God, His character, & the bible? If not, why not?

#2 Starter

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Posted 18 March 2010 - 07:38 PM

The E. Coli long-term evolution experiment is an ongoing study led by Richard Lenski. The study tracks genetic changes in 12 initially nearly identical populations of asexual Escherichia coli bacteria. The experiment started on February 24, 1988 and on February 14, 2010 the populations reached the milestone of 50,000 generations.
QUESTIONS:
What implications does this study have on the (Darwinian) Theory of Evolution?

Evolution Supporters

a.) For those of you who are familiar with this study, is it possible that the adaptations in this study were simply the result of recessive or dormant genes that were already present?

b.) How do you prove empirically that an adaptation is *actually* an adaptation (creating new genetic information) and not a case of dormant or recessive genes?   
Evolution Opposers

a.) There is a New Theory of Evolution. Is it possible for this "new" theory to be both accurate and in line with God, His character, & the bible? If not, why not?

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The Topic should be: Does the E. Coli Long Term Evolution Experiment Support Evolution?

It seems that I screwed something up. Sorry for the mix up.

#3 AFJ

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Posted 18 March 2010 - 07:43 PM

The E. Coli long-term evolution experiment is an ongoing study led by Richard Lenski. The study tracks genetic changes in 12 initially nearly identical populations of asexual Escherichia coli bacteria. The experiment started on February 24, 1988 and on February 14, 2010 the populations reached the milestone of 50,000 generations.
QUESTIONS:
What implications does this study have on the (Darwinian) Theory of Evolution?

Evolution Supporters

a.) For those of you who are familiar with this study, is it possible that the adaptations in this study were simply recessive or dormant?

b.) How do you prove empirically that an adaptation is *actually* an adaptation and not a case of dormant or recessive genes?   
Evolution Opposers

a.) There is a New Theory of Evolution. Is it possible for this hypothesis to be both accurate and in line with God, His character, & the bible? If not, why not?

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It's late so I don't have time to reference. But from my study of it-- wild type E.Coli are not able to digest citrate. An environment was set up and they were basically force fed citrate. Now the selected bacteria can digest it.

The thing that is not advertised is the cell wall elongation it caused (among other things), which is detrimental in other environments--it basically handicapped the bacteria, and their fitness level dropped. This is called ecological specialization.

In that their fitness declined, I would tend to think this is opposite of Darwinian evolution. Survival to the fittest. I understand selection also selects lower fit organisms through genetic drift, but the overall goal of evolution is to evolve by causing new and more complex alleomorphic features.

In studying bacteria, one can see they are designed for adaptation. Plasmids and HGT are beyond coincidence--they are made to fit, and the fit causes adaptation in different environments.

#4 Fedora

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Posted 18 March 2010 - 07:54 PM

It's late so I don't have time to reference.  But from my study of it--E.Coli are not supposed to be able to digest citrate.  An environment was set up and they were basically force fed citrate. Now the selected bacteria can now digest it.

The thing that is not advertised is the cell wall elongation it caused (among other things), which is detrimental in other environments--it basically handicapped the bacteria, and their fitness level dropped.  This is called ecological specialization. 

In that their fitness declined, I would tend to think this is opposite of Darwinian evolution.  Survival to the fittest.  I understand selection also selects lower fit organisms through genetic drift, but the overall goal of evolution is to evolve by causing new and more complex alleomorphic features.

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The bacteria did exactly what is predicted, they became specialized to their environment. That may cause, by extension, a loss of ability to survive in a separate environment.

#5 AFJ

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Posted 18 March 2010 - 08:00 PM

The bacteria did exactly what is predicted, they became specialized to their environment. That may cause, by extension, a loss of ability to survive in a separate environment.

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A prediction is limited to a particular hypothesis. What was the hypothesis?

Evolution in general predicts that a bacteria should change into another organism. Adaptation is not evolution.

#6 Fedora

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Posted 18 March 2010 - 08:05 PM

A prediction is limited to a particular hypothesis.  What was the hypothesis? 

Evolution in general predicts that a bacteria should change into another organism.  Adaptation is not evolution.

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Yes, it is. Evolution is the change in allele frequencies in a population through time. The THEORY of evolution speaks of speciation, etc. etc.

And, a hypothesis could be (I haven't studied this research) that the Bacteria would evolve to suit their new environment. They did just that.

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Posted 18 March 2010 - 08:38 PM

Evolution Supporters

a.) For those of you who are familiar with this study, is it possible that the adaptations in this study were simply the result of recessive or dormant genes that were already present?

b.) How do you prove empirically that an adaptation is *actually* an adaptation (creating new genetic information) and not a case of dormant or recessive genes?


Adaptation has been observed in populations bred from one bacterium.

a.) There is a New Theory of Evolution.

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This is not new, just another empty information claim.

#8 Bruce V.

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Posted 18 March 2010 - 10:08 PM

a.) There is a New Theory of Evolution. Is it possible for this "new" theory to be both accurate and in line with God, His character, & the bible? If not, why not?

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Shapiro is an interesting Scientist. He doesn't believe either evolution or I.D. entirely. He sees both sides and has bones to pick with each side.

I like this post.

A cell under stress will splice its own DNA into over 100,000 pieces. Then a program senses hundreds of variables in its environment and then re-arranges those pieces to produce a new, better, evolved cell.


Shapiro knows what is going on is not evolution so he made up his own theory. I listened to him for about an hour about spontaneous regeneration. Very interesting stuff.

#9 Bruce V.

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Posted 18 March 2010 - 10:14 PM

It's late so I don't have time to reference.  But from my study of it-- wild type E.Coli are not able to digest citrate.  An environment was set up and they were basically force fed citrate. Now the selected bacteria can digest it.

The thing that is not advertised is the cell wall elongation it caused (among other things), which is detrimental in other environments--it basically handicapped the bacteria, and their fitness level dropped.  This is called ecological specialization. 

In that their fitness declined, I would tend to think this is opposite of Darwinian evolution.  Survival to the fittest.  I understand selection also selects lower fit organisms through genetic drift, but the overall goal of evolution is to evolve by causing new and more complex alleomorphic features. 

In studying bacteria, one can see they are designed for adaptation.  Plasmids and HGT are beyond coincidence--they are made to fit, and the fit causes adaptation in different environments.

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We have debated the e-coli citric acid issue before.

Lenski was using his computer program Availa (sp) and he reversed engineered the sequence. He know what mutations were required. They save e-coli, by freezing, they have been testing. One old patch had 2 of the 3 mutations needed to digest citric acid. So he force feed citric acid to this strain until the last mutation came about.

Bruce

#10 jason777

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Posted 19 March 2010 - 04:38 AM

I heard that all E. coli can digest citrate in low oxygen (no mutation needed). perhaps they suddenly adapted at a certain generation because some kind of vaccum prevented oxygen from reaching the sample overnight.

#11 Yorzhik

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Posted 19 March 2010 - 05:19 AM

Yes, it is. Evolution is the change in allele frequencies in a population through time. The THEORY of evolution speaks of speciation, etc. etc.

So if there were no mutations, would there be evolution?

And, a hypothesis could be (I haven't studied this research) that the Bacteria would evolve to suit their new environment. They did just that.

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That's fine. But what was the mechanism it took to achieve this feat? Was it mutations? Which ones?

#12 AFJ

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Posted 19 March 2010 - 06:37 PM

Yes, it is. Evolution is the change in allele frequencies in a population through time. The THEORY of evolution speaks of speciation, etc. etc.

And, a hypothesis could be (I haven't studied this research) that the Bacteria would evolve to suit their new environment. They did just that.

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If you can take the time to open your mind and read this. It's not macro evolution Fedora. It's adaptive evolution. Creationists accept this.

--Bacteria already adapt to different environments and resources. They can go from digesting glucose to maltose without a decrease in fitness. There are many different plasmids and other bacteria which can transfer genes. The bacteria accept them, incorporate the genes and the phenotype can change.

This is where you need to pay attention. If a phage (virus) comes to incorporate it's DNA, the bacteria has enzymes which destroy it's DNA. Of course, some don't and that's how viruses multiply. Suppose you tell me what caused such discerning enzymes.

Now take the two scenarios. If you want you can ignore any possibility of design and purpose. But if you choose to say it happened by random processes--you have no empirical data to back what you say. No one has EVER seen the enzymes which destroy DNA and ignore other DNA be originally coded for, nor saw how that happened.

No one has ever seen the viruses evolve nor the bacteria, nor, more importantly, how plasmids and bacteria evolved--a symbiotic relationship. Meaning they had to evolve together. The only problem is that plasmids would need an entirely evolved bacteria to be of any importance (they are not actually alive), but for the bacteria--they need plasmids NOW. Not in a million years!

#13 Fedora

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Posted 19 March 2010 - 07:41 PM

If you can take the time to open your mind and read this.  It's not macro evolution Fedora.  It's adaptive evolution.  Creationists accept this.

--Bacteria already adapt to different environments and resources.  They can go from digesting glucose to maltose without a decrease in fitness.  There are many different plasmids and other bacteria which can transfer genes.  The bacteria accept them, incorporate the genes and the phenotype can change.

This is where you need to pay attention.  If a phage (virus) comes to incorporate it's DNA, the bacteria has enzymes which destroy it's DNA.  Of course, some don't and that's how viruses multiply.  Suppose you tell me what caused such discerning enzymes. 

Now take the two scenarios.  If you want you can ignore any possibility of design and purpose. But if you choose to say it happened by random processes--you have no empirical data to back what you say. No one has EVER seen the enzymes which destroy DNA and ignore other DNA be originally coded for, nor saw how that happened. 

No one has ever seen the viruses evolve nor the bacteria, nor, more importantly, how plasmids and bacteria evolved--a symbiotic relationship.   Meaning they had to evolve together. The only problem is that plasmids would need an entirely evolved bacteria to be of any importance (they are not actually alive), but for the bacteria--they need plasmids NOW.  Not in a million years!

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I know it isn't "Macro" evolution, I made that distinction in the beginning. And, would you mind defining Macro evolution for me?

A symbiotic relationship could evolve quite easily. If the bacteria were to evolve an enzyme which simply destroyed all foreign DNA, it could have then became specialized to accept only the beneficial DNA of the specific plasmid.

That said, I have not specifically researched the relationship of Plasmids and bacteria, Evolution does not NEED to know how every single evolutionary change occurred. Even so, scientists should work towards understanding as much as possible, and they are doing so. But you cannot show a single hole in present knowledge and say that there is no conceivable way for the organism (or whatever you bring up) to have evolved.

And, I find it extremely ironic that you ask for empirical evidence for EVERY SINGLE occurrence of evolution. I ask you, please tell me HOW God created life, each piece of life, and provide empirical, testable, evidence for all of it.

This is ignoring your criteria that the process must be observed which, if levied at evolution, MUST be levied at creation as well.

#14 AFJ

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Posted 20 March 2010 - 06:53 AM

I know it isn't "Macro" evolution, I made that distinction in the beginning. And, would you mind defining Macro evolution for me?

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I would love to, but first let me ask you to imagine a new biological apparatus which could evolve in us. It must be new. It can't be wings--that's already been done and would be convergent. It can't be radar or sonar ability--that would be convergent.

You have to think up something new and then tell me how the genes are going to sequence in order to produce properly folding, interlocking proteins--with, of course the genes for the corresponding regulatory proteins. You need to give the code for the appropriate signal proteins which will work with transcription factors to turn all the genes on and off at the appropriate times-- so the body doesn't spend all it's ATP overproducing your new biological apparatus.

Don't forget, you already have the golgi appuratus to further reshape and store your new proteins, and you have current transcription and translation processes, along with transcription factors, and replication fork enzymes. So you have head start.

You should have no problems giving me the codes and we will have this new biological appuratus up and running in no time.

What? You can't do that? Why? I mean according to you it's so simple that random processes did it with NO brain. And you have a brain. So WHY can't you do it?

But that is what macro evolution says happened, so it must be possible.


A symbiotic relationship could evolve quite easily. If the bacteria were to evolve an enzyme which simply destroyed all foreign DNA, it could have then became specialized to accept only the beneficial DNA of the specific plasmid.

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Quite easily? You're borrowing from what already exists to insufficiently explain a process you haven't studied.

1. You didn't understand my question. What causes the bacteria to discern what is 'foreign?' I mean it's a one cell. It has no capacity to care if a bacteriophage begins using it's machinery to produce it's DNA and then explode the cell. It's random, so the process would be a series of spontaneous chemical reactions. Nothing is going to guide it, so therefore--the enzyme was made randomly. Not in any response to the fact that the phage's DNA would kill it. THAT, my friend would imply reasoning.

2. An evolving enzyme?--it needed to be there from the beginning or bacteria would be extinct. That is the viruses would kill the bacteria and they would be extinct also, having no more bacteria. So that leaves just one thing. The viruses just happened to evolve DNA which would just happen to cause the randomly evolved enzyme to respond by chemically cutting it up.

That is they had to be isolated and evolve separately to chemically match, before they ever met. I hope you understand this. The alternative is that viruses would kill bacteria.

#15 deadlock

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Posted 20 March 2010 - 07:47 AM

The E. Coli long-term evolution experiment is an ongoing study led by Richard Lenski. The study tracks genetic changes in 12 initially nearly identical populations of asexual Escherichia coli bacteria. The experiment started on February 24, 1988 and on February 14, 2010 the populations reached the milestone of 50,000 generations.
QUESTIONS:
What implications does this study have on the (Darwinian) Theory of Evolution?

Evolution Supporters

a.) For those of you who are familiar with this study, is it possible that the adaptations in this study were simply the result of recessive or dormant genes that were already present?

b.) How do you prove empirically that an adaptation is *actually* an adaptation (creating new genetic information) and not a case of dormant or recessive genes?   
Evolution Opposers

a.) There is a New Theory of Evolution. Is it possible for this "new" theory to be both accurate and in line with God, His character, & the bible? If not, why not?

View Post


Wild E. coli already has a number of enzymes that normally use citrate and can digest it (it’s not some exotic chemical the bacterium has never seen before). However, the wild bacterium lacks an enzyme called a “citrate permease” which can transport citrate from outside the cell through the cell’s membrane into its interior. So all the bacterium needed to do to use citrate was to find a way to get it into the cell. The rest of the machinery for its metabolism was already there. As Lenski put it, “The only known barrier to aerobic growth on citrate is its inability to transport citrate under oxic conditions.”

Other workers (cited by Lenski) in the past several decades have also identified mutant E. coli that could use citrate as a food source. In one instance the mutation wasn’t tracked down. In another instance a protein coded by a gene called citT, which normally transports citrate in the absence of oxygen, was overexpressed. The overexpressed protein allowed E. coli to grow on citrate in the presence of oxygen. It seems likely that Lenski’s mutant will turn out to be either this gene or another of the bacterium’s citrate-using genes, tweaked a bit to allow it to transport citrate in the presence of oxygen.

The major point Lenski emphasizes in the paper is the historical contingency of the new ability. It took trillions of cells and 30,000 generations to develop it, and only one of a dozen lines of cells did so. What’s more, Lenski carefully went back to cells from the same line he had frozen away after evolving for fewer generations and showed that, for the most part, only cells that had evolved at least 20,000 generations could give rise to the citrate-using mutation. From this he deduced that a previous, lucky mutation had arisen in the one line, a mutation which was needed before a second mutation could give rise to the new ability. The other lines of cells hadn’t acquired the first, necessary, lucky, “potentiating” mutation, so they couldn’t go on to develop the second mutation that allows citrate use. Lenski argues this supports the view of the late Steven Jay Gould that evolution is quirky and full of contingency. Chance mutations can push the path of evolution one way or another, and if the “tape of life” on earth were re-wound, it’s very likely evolution would take a completely different path than it has.

I think the results fit a lot more easily into the viewpoint of The Edge of Evolution. One of the major points of the book was that if only one mutation is needed to confer some ability, then Darwinian evolution has little problem finding it. But if more than one is needed, the probability of getting all the right ones grows exponentially worse. “If two mutations have to occur before there is a net beneficial effect — if an intermediate state is harmful, or less fit than the starting state — then there is already a big evolutionary problem.” And what if more than two are needed? The task quickly gets out of reach of random mutation.

Multiple Mutations Needed for E. Coli

#16 Guest_DNAunion_*

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Posted 20 March 2010 - 09:59 PM

a.) For those of you who are familiar with this study, is it possible that the adaptations in this study were simply the result of recessive or dormant genes that were already present?


1. "Recessive" means that when 2 different alleles for a gene at a given locus are present, the expression effect of one of them (the recessive) is not seen. E. coli have only 1 chromosome, and so only 1 allele for any given locus, so "recessive" does not apply.

2. Billions of mutations occurred, more than enough to mutate every nucleotide in the E. coli genome multiple times. Yet the ability to import citrate arose in only 1 line. If it were just a matter of a "sleeping" gene being "reawakened" by a change to its regulation, with all mutations having occurred multiple times, it should have occurred in all lines, not just one. You would really need to be more specific if you want a better answer.


b.) How do you prove empirically that an adaptation is *actually* an adaptation (creating new genetic information) and not a case of dormant or recessive genes?   


1. Recessive doesn't apply, as I stated above.

2. You need to give a scenario for a "dormant" gene being "reawakened."

#17 Guest_DNAunion_*

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Posted 20 March 2010 - 10:44 PM

If a phage (virus) comes to incorporate it's DNA, the bacteria has enzymes which destroy it's DNA.  Of course, some don't and that's how viruses multiply.  Suppose you tell me what caused such discerning enzymes. 


What about putting the shoe on the other foot?
If the bacteria were Intelligently Designed, as you suggest, then why would they blindly process the DNA of a lytic virus, since doing so is going to lead to bacterium's destruction? Why do our own human cells blindly process the DNA or RNA of viruses??


PS: Bacterial restriction enzymes do not recognize the viral DNA as being from a virus: it's not like the enzymes actually discern the source of the DNA. The reason the bacterial DNA is not digested by its own enzymes is that some of the bacterial adenines and cytosines are methylated. Other than that, DNA from any source - even human made - is digested by the restriction endonucleases.


No one has ever seen the viruses evolve nor the bacteria, nor, more importantly, how plasmids and bacteria evolved--a symbiotic relationship.  


That is a misuse of the term 'symbiotic'. Symbiosis requires (at least) 2 living organisms, and a plasmid is not a living organism ... as even you later state.



The only problem is that plasmids would need an entirely evolved bacteria to be of any importance (they are not actually alive), but for the bacteria--they need plasmids NOW.  Not in a million years!


Except that (1) not all bacterial species have plasmids, and (2) of the bacterial species that do have plasmids, plasmids are not usually required under normal conditions ...

Plasmids usually contain from 5 to 100 genes that are generally not crucial for the survival of the bacterium under normal enviornmental conditions; plasmids may be gained or lose without harming the cell.

(Microbiology: An Introduction: 9th Edition. Tortora, Funke, & Case. Pearson / Benjamin Cummings. 2007, p95)



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Posted 20 March 2010 - 11:01 PM

You have to think up something new and then tell me how the genes are going to sequence in order to produce properly folding, interlocking proteins--with, of course the genes for the corresponding regulatory proteins.  You need to give the code for the appropriate signal proteins which will work with transcription factors to turn all the genes on and off at the appropriate times-- so the body doesn't spend all it's ATP overproducing your new biological apparatus. 


But evolution usually works by modifications in what is already "laying around," not by inventing things from scratch. Look at your arms and hands, and your legs and feet. They were not new structures, arisen de novo from nothing. Their ultimate origin can be traced back more than 370 million years to the paired fins of fish (and probably before that, to the unpaired medial fins of fish, and before that, possibly to the gill/branchial rays of even earlier fish).

Suppose you asked someone to explain the origin of human hands. Do you really expect a person on the Internet to invest the time and effort to learn and describe every molecular step in a process that required several hundred million years to occur? Quite unreasonable.

But that's not what you are asking: you are asking for something even less reasonable! You are asking for someone to whip up out of thin air some novelty, on the scale of human hands, that does not even exist! And then to explain every single step in how this imaginary thing could come to exist! Not reasonable.

#19 AFJ

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Posted 21 March 2010 - 06:43 AM

But evolution usually works by modifications in what is already "laying around," not by inventing things from scratch.  Look at your arms and hands, and your legs and feet.  They were not new structures, arisen de novo from nothing.  Their ultimate origin can be traced back more than 370 million years to the paired fins of fish (and probably before that, to the unpaired medial fins of fish, and before that, possibly to the gill/branchial rays of even earlier fish). 

Suppose you asked someone to explain the origin of human hands.  Do you really expect a person on the Internet to invest the time and effort to learn and describe every molecular step in a process that required several hundred million years to occur?  Quite unreasonable.

But that's not what you are asking: you are asking for something even less reasonable!  You are asking for someone to whip up out of thin air some novelty, on the scale of human hands, that does not even exist!  And then to explain every single step in how this imaginary thing could come to exist!  Not reasonable.

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I didn't expect an answer, DNAunion. Everyone knows that's impossible. I asked it to make a point: Random processes, even in response to environment, can't produce new information in the genome -they can only take away or duplicate. Please let me back up my point...

Here's the beginning statement in your post:

DNAunion...
But evolution usually works by modifications in what is already "laying around," not by inventing things from scratch. 


Thank you. That's the entire point! Any kind of change in organisms requires something that is "already 'laying around.'" But all present empirical research of adaptive mutation shows loss or duplication in genetic machinery or phenotypical features.

Duplication--Look at drosophylla. Legs on the head, and extra wings--heralded as evolution in action. But what is it? Duplication of pre-existing anatomical parts. Basically a degenerative defect, as many of these flies are blind, the legs do not move, and the wings do not help flight. There is no added information.

Deformation of structure--Look at sickle cell, which alters the shape of red blood cells. A response to malaria. The mutation is beneficial in Africa where there is alot of malaria. But it goes without saying that overall it is degenerative, in that the trait from both sides shortens lifespan substantially.

Deletion of systems

Look at bacteria:

A Creationist Perspective of Beneficial Mutations in Bacteria
by Kevin L. Anderson, PhD, and Georgia Purdom, PhD

Mutations alter the nucleotide sequence of the DNA. They may affect the organism’s phenotype, which can play a key role in bacterial adaptation and transformation to changing environments. Some of these mutations even appear to be beneficial to the organism....

In bacteria, a wide range of mutations can be shown to provide a beneficial phenotype to the cell. These benefits are often of sufficient phenotypic affect that they can undergo strong positive selection.  But the benefits are generally temporary and limited....

Each of these examples, as well as numerous others, involves certain environmental conditions that make these mutations phenotypically beneficial. However, these mutations frequently eliminate or reduce pre-existing cellular systems and functions. This has been referred to as antagonistic pleiotropy; meaning the cell experiences a trade-off where a temporary benefit for surviving one environmental condition is provided at the expense of systems used for other environments. If the environmental conditions change, the mutation usually becomes less beneficial and perhaps even detrimental. Hence, these mutations do not provide a genetic mechanism that accounts for the origin of biological systems or functions. Rather, they require the prior existence of the targeted cellular systems.


The evolution we can see does not add--it only adapts by loss or deformity.

...these mutations do not provide a genetic mechanism that accounts for the origin of biological systems or functions. Rather, they require the prior existence of the targeted cellular systems.


It shows that the entire concept of evolution is flawed. The theory itself rather borrows from what is there, already finished, and attributes another cause.

I would say the entire science of evolution is "knowledge" taking glory from what God spoke into being.

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Posted 21 March 2010 - 07:27 AM

I asked it to make a point: Random processes, even in response to environment, can't produce new information in the genome -they can only take away or duplicate.


But evolution is not just random processes: it involves non-random natural selection operating cumulatively on top of random (with respect to fitness) genetic mutations.



That's the entire point!  Any kind of change in organisms requires something that is "already 'laying around.'"  But all present empirical  research of adaptive mutation shows loss or duplication in genetic machinery or phenotypical features. 


There are several processes that can add genetic information to genomes, two of which are (a) gene duplication followed by divergence and (2) exon shuffling.


(1) Gene duplication followed by divergence
A gene gets duplicated (by unequal crossing over, for example) and then one copy accumulates mutations, hitting upon a new functional sequence that performs a new or related function.

As an explanatory analogy:

Gene A
TOWER

Gene A gets duplicated
TOWER TOWER

One copy is mutated to a new, functional sequence
TOWER POWER





A gene family consists of a group of related genes, and arises by multiple rounds of duplication and divergence.

Gene A
TOWER

Gene A gets duplicated
TOWER TOWER

One copy is mutated to a new, functional sequence
TOWER POWER

Gene B gets duplicated
TOWER POWER POWER

One copy of Gene B is mutated to a new, functional sequence
TOWER POWER POKER

Gene A gets duplicated
TOWER TOWER POWER POKER

One copy of Gene A is mutated to a new, functional sequence
TOWER TOWED POWER POKER

Gene D gets duplicated
TOWER TOWED POWER POKER POKER

One copy of Gene D is mutated to a new, functional sequence
TOWER TOWED POWER POKER JOKER




(2) Exon shuffling
Most genes in animals do not consist of a single, continuous sequence of coding nucleotides: instead, they consist of a series of multiple exons (exported regions) separated by introns (intervening sequences that are spliced out). In many cases, and single exon codes for a functional domain, such as a protein fold that binds to DNA. Exons can get "shuffled" around in the genomes, producing new combinations of new genes with a new set of functional folds.

As an explanatory example:

Starting genome, with exons separated by ---.
ADORN---MENT
IM---POSSIBLE
PROVE

The IM exon is shuffled in front of the PROVE exon.
ADORN---MENT
IM---POSSIBLE
IM---PROVE

The MENT exon is shuffled to the back of the PROVE exon.
ADORN---MENT
IM---POSSIBLE
IM---PROVE---MENT

Thus PROVE has become IMPROVEMENT (note that alternate splicing could retain all three forms: PROVE, IMPROVE, and IMPROVEMENT).




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