"Adaptive evolution"

[shernren]

There are a number of things that I will touch on briefly. Changes in gene expression, genes can be turned on and off, chromosomal rearrangements.

You might want to know that chromosomal rearrangements are mutations.

I'm more than happy to talk about this. We could start with the question:

Are changes in gene expression, or "genes being turned on and off", heritable?

(I hope you can see the relevance of this question. I'm sure you'll agree with me that any change to a genome that isn't heritable can't, by definition, go into defining the differences between species.)

 

[Notedstrangeperson]

[Don't mind me hijacking your thread]

Epigenetics (definition from the university of Utah):

The development and maintenance of an organism is orchestrated by a set of chemical reactions that switch parts of the genome off and on at strategic times and locations. Epigenetics is the study of these reactions and the factors that influence them.

Genes can also be switched on or off depending on environmental factors such as what we eat, how much stress we are exposed to or parental care. One famous study from New Zealand looked at a combination of genes and family violence, finding that children who had been abused AND a 'weak' version of a gene which controls neurotransmitter regulation were twice as likely to become violent criminals than other children. Put simply, the gene's violent tendacies had been 'actived' by the abuse.

Epigenetics has not played a big part in evolution as it was believed that these changes could not be passed on. However recently there has been some studies showing that epigenetic changes can be inherited. This would mean that adaptive evolution could be attributed to how our parents lives their lives - not just unpredictable genetic changes. But so far the evidence is scant at best.

What (if any) effect would this have on the Creationism / Evolution debate?

 

[shernren]

I agree that the epigenetics article makes for very interesting reading. Does it modify evolution? I suppose it does, somewhat.

But there are two important ways in which epigenetic changes are inheritable. To see this, let's suppose I was one of the potential fathers who had smoked before I was 11, in the final study mentioned. Now, presumably the smoking causes a certain section of my DNA to be methylated. But how did that methylation occur? It doesn't magically happen, and the nicotine smoke sure never goes anywhere near my delicate reproductive regions.

In other words, there is some biological mechanism that methylates a section of my DNA if I smoke more. And since that biological mechanism is produced by a section of my genome, that means that there is a gene for "if I smoke more, section so-and-so of my DNA will be methylated". (Of course, that's grossly oversimplified language - what I really mean is that there is a gene complex, which is expressed in a certain way in certain parts of the body, which produces proteins that have the effect of ... but that's a lot to type.) But that gene is a gene that can be selected for. Presumably, there could be a possible variant of that gene which allows men to smoke like a fish and not suffer any epigenetic damage at all.

But I don't have that variant, so a segment of my genome has been epigenetically marked. However, let's suppose that segment of the genome was never, ever read by my ribosomes to produce any proteins. Maybe it's a segment of junk DNA that gets marked. In that case, the epigenetic modification would have no effect whatsoever on me or on any of my offspring.

As such, there must be a biological mechanism that actually reads that section of DNA, which is modified accordingly when epigenetic modifications are present. And again, there must be genes for that to happen.

In summary: there must be genes that code for epigenetic modifications, and genes that code for those modifications to be read. But these are heritable genes which can be selected for or against just like any other old gene. So epigenetics doesn't invalidate natural selection, it just pushes it one step up.

That's in theory, of course. In practice, epigenetic machinery is probably highly conserved at least in mammals if not in multicellular organisms. Something that tinkers around so severely with DNA expression is probably going to be very tightly regulated. But that's just a matter of historical contingency, though; if the environmental pressures were high enough, alternate epigenetic systems would probably emerge which could be selected between, so that epigenetics would indeed come under natural selection.

 

[mark kennedy]

You might want to know that chromosomal rearrangements are mutations.

I'm more than happy to talk about this. We could start with the question:

Are changes in gene expression, or "genes being turned on and off", heritable?

(I hope you can see the relevance of this question. I'm sure you'll agree with me that any change to a genome that isn't heritable can't, by definition, go into defining the differences between species.)

I found the thread late but did some reading on the subject. It looks like gene regulation changes are the key, I found several papers in PLoS on the subject. Yes, as far as I can tell they can be heritable or they might just be noise.

Errors in information transfer from DNA to RNA to protein are inevitable and ubiquitous. When errors that occur in DNA are not repaired and become fixed as permanent mutations, they can have heritable phenotypic consequences for cells. In contrast, errors that occur during RNA transcription are considered transient, because the life span of mRNAs and their encoded proteins is thought to be too short to have heritable consequences. Here, we show that transient errors that arise during transcription can cause a heritable phenotypic change within a population of genetically identical Escherichia coli cells growing in the same environment. Transcriptional Infidelity Promotes Heritable Phenotypic Change in a Bistable Gene Network ​

Yes chromosomal rearrangements are mutations and BTW, transcript errors are mutations and apparently heritable. I don't know where you are trying to go with this but I'll check the thread later.

 

[shernren]

Oh hi! I have no idea where I am going with this thread. I'm glad you found it, though. This is really your thread. See, you're always complaining about how evolutionists are constantly trying to correct your use of terminology, technical details, etc. And you say that you have interesting issues concerning adaptive evolution which you want to discuss with people.

So here's the deal. All technical corrections on this thread will be replaced with smilies.

How does that sound? For example, instead of me pointing out that the very paper you cited considers transcription errors separately from mutations in at least a dozen different sentences, I'll just say this:

"Transcription errors are mutations? "

and see if I have helpful, non-ego-deflating answers to any questions you have to pose.

So go ahead, ask anything you're curious about concerning adaptive evolution, "molecular mechanisms", etc.

(Of course, I suspect that this thread will eventually degenerate into a smorgasbord of smilies, but I'm a scientist, and we test our suspicions.)

 

[mark kennedy]

Oh hi! I have no idea where I am going with this thread. I'm glad you found it, though. This is really your thread. See, you're always complaining about how evolutionists are constantly trying to correct your use of terminology, technical details, etc. And you say that you have interesting issues concerning adaptive evolution which you want to discuss with people.

So here's the deal. All technical corrections on this thread will be replaced with smilies.

How does that sound? For example, instead of me pointing out that the very paper you cited considers transcription errors separately from mutations in at least a dozen different sentences, I'll just say this:

"Transcription errors are mutations? "

Whatever, I mean thats just what the section I quoted said. You have a real talent for ignoring things right in front of you

and see if I have helpful, non-ego-deflating answers to any questions you have to pose.

So go ahead, ask anything you're curious about concerning adaptive evolution, "molecular mechanisms", etc.

(Of course, I suspect that this thread will eventually degenerate into a smorgasbord of smilies, but I'm a scientist, and we test our suspicions.)

Maybe if you focused on the topic ... it's your show shern, I'm just a passer by throwing nickles in the hat while there's nothing better to do..

 

[shernren]