Exploring Lamarckian Evolution - Mike Olsen

[That Neuron]

Yes we are all taught today that Lamarck and his crazy idea are hogwash, true I suppose, but his idea, that all animals are influenced by their environment in a designed way, opens up a simple idea.

Lets take a hypothetical Bacterium that produces a compound that degrades penicillin, the production of this certain compound is regulated (epigenetically) by a cascade mechanism, triggered by the presence of penicillin. So in other words, when exposed to Penicillin the bacteria produces our fictional enzyme 'Penicillinase'. The expression of the gene that encodes penicillinase ultimately takes its toll on the gene, by increasing the amount of double strand breaks, and repairs on that particular gene... Increasing its rate of mutation. So when the bacterium is exposed to penicillin, the gene that produces penicillinase mutates at a faster rate than the same gene in a bacterium in a penicillin-free environment.

So an organism (possessing cellular mechanisms that regulate its genetic expression based on external stimuli) is influenced by its environment in the rate of mutation of certain genes... so our lamarckian giraffe may not have offspring with longer necks... but offspring with necks of greater variability.

Of course this is limited to microorganisms and gametes, (somatic mutations are not inherited) but still worth putting it out there!

Thanks!

Mike Olsen

 

[Ryan_m_b]

Yes we are all taught today that Lamarck and his crazy idea are hogwash, true I suppose, but his idea, that all animals are influenced by their environment in a designed way, opens up a simple idea.

Lets take a hypothetical Bacterium that produces a compound that degrades penicillin, the production of this certain compound is regulated (epigenetically) by a cascade mechanism, triggered by the presence of penicillin. So in other words, when exposed to Penicillin the bacteria produces our fictional enzyme 'Penicillinase'. The expression of the gene that encodes penicillinase ultimately takes its toll on the gene, by increasing the amount of double strand breaks, and repairs on that particular gene... Increasing its rate of mutation. So when the bacterium is exposed to penicillin, the gene that produces penicillinase mutates at a faster rate than the same gene in a bacterium in a penicillin-free environment.

So an organism (possessing cellular mechanisms that regulate its genetic expression based on external stimuli) is influenced by its environment in the rate of mutation of certain genes... so our lamarckian giraffe may not have offspring with longer necks... but offspring with necks of greater variability.

Lamarck's ideas focussed around gross anatomy. Essentially Lamarckian evolution could be conceptualised as inheritance of http://en.wikipedia.org/wiki/Phenome" over genome. Why do you think that increased gene expression leads to increased mutation of that gene?

 

[That Neuron]

Yes... It is not lamarkism... I just thought that was the most similar idea to it... so I used that Idea. But more importantly, I thought that a form of tautomerism would be increased through increased expression, this would later cause a mutation during replication.

 

[Ryan_m_b]

I thought that a form of tautomerism would be increased through increased expression, this would later cause a mutation during replication.

I think you mean increased chance during replication http://en.wikipedia.org/wiki/Mutation#Spontaneous_mutation. I've never heard of gene expression increasing the chance of mutation though I could just have never come across it (which I would rate as unlikely).

 

[That Neuron]

I think you mean increased chance during replication http://en.wikipedia.org/wiki/Mutation#Spontaneous_mutation. I've never heard of gene expression increasing the chance of mutation though I could just have never come across it (which I would rate as unlikely).

Yes that is what I was referring to, I was under the impression that DNA helicase increases the rate of misplacing hydrogen bonding (and probably other spontaneous mutations) by opening up the helix... allowing access of other mutation causing molecules... Since repeated transcription would do this... I would suspect that it would result in increased mutation?

 

[Ryan_m_b]

Yes that is what I was referring to, I was under the impression that DNA helicase increases the rate of misplacing hydrogen bonding (and probably other spontaneous mutations) by opening up the helix... allowing access of other mutation causing molecules... Since repeated transcription would do this... I would suspect that it would result in increased mutation?

I've not heard of helicase increasing the chance of misplacing hydrogen bonding, nor of increasing the chance of inducible or spontaneous mutation. Perhaps another member can enlighten us.

 

[jambaugh]

I don't think environmental effects on mutation rate count as Lamarckian evolution.

However a common truism of agriculture is seeds for certain crops grown in a altered climate thrive better than their parent plants in that climate. I recall this in reading up on growing tobacco. The seed supplier suggested improved yield from 2nd generation seeds.
(... quick google search...)
Here's a study on http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2486.1998.00184.x/abstract" .

Now I don't know if there is any genetic level adaptation or rather it is a matter of built in genetic behavior, where the parent plant produces enzymes in the seed fruit which better prepares the child plant for specific climate, or what. But it might be a hint of Lamarck's idea.

 

[Galteeth]

Might find the work of Eric Richards interesting.http://news.wustl.edu/news/Pages/7408.aspx

 

[mishrashubham]

Yes that is what I was referring to, I was under the impression that DNA helicase increases the rate of misplacing hydrogen bonding (and probably other spontaneous mutations) by opening up the helix... allowing access of other mutation causing molecules... Since repeated transcription would do this... I would suspect that it would result in increased mutation?

Yes you are right in saying that transciption can cause mutations, the term for which is Transcription-Associated-Mutations (TAM). However I don't think the precise mechanism for this is known, although there are indications that the longer DNA is exposed to DNA dmaging agents the better are the chances of mutation (since ssDNA is much more susceptible to these agents). And I suppose this supports your statement although your proposed mechanism regarding helicases might be purely hypothetical. I'll post links to peer reviewed literature on TAMs later when I have access to my laptop.

 

[That Neuron]

I don't think environmental effects on mutation rate count as Lamarckian evolution.

No, environmental effects shouldn't be counted as lamarkism when they effect the rate of mutation of the genome as a whole, however when environmental effects change the mutation rates of specific genes linked to the environmental effect... I would call it a form of lamarkism, probably not the definition of lamarkism... but similar.

However a common truism of agriculture is seeds for certain crops grown in a altered climate thrive better than their parent plants in that climate. I recall this in reading up on growing tobacco. The seed supplier suggested improved yield from 2nd generation seeds.
(... quick google search...)
Here's a study on http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2486.1998.00184.x/abstract" .

Now I don't know if there is any genetic level adaptation or rather it is a matter of built in genetic behavior, where the parent plant produces enzymes in the seed fruit which better prepares the child plant for specific climate, or what. But it might be a hint of Lamarck's idea.

Yes that is very interesting! It doesn't help my little theory much because I think that the processes that determine the adaptation to climate are produced via natural selection, even if they take a generation or two to take effect... But still I found it fascinating!

Might find the work of Eric Richards interesting.


http://news.wustl.edu/news/Pages/7408.aspx

Yeah! I read it, it was interesting, I don't think he was focusing on the mutation rates, more on the epigenetic processes that cause short term soft inheritance... but still Really cool, thanks for the link!

Yes you are right in saying that transciption can cause mutations, the term for which is Transcription-Associated-Mutations (TAM). However I don't think the precise mechanism for this is known, although there are indications that the longer DNA is exposed to DNA dmaging agents the better are the chances of mutation (since ssDNA is much more susceptible to these agents). And I suppose this supports your statement although your proposed mechanism regarding helicases might be purely hypothetical. I'll post links to peer reviewed literature on TAMs later when I have access to my laptop.

Yes my mechanism regarding helicases was entirely hypothetical, It just seemed intuitive to me that helicases and Polymearases would increase the rate of hydrogen mishaps, over that of stagnant DNA. But I think it does make sense that opening a strand of DNA would make it's internal hydrogen bonds avaliable to mutagens... Anyways I'd love to see some of those articles, I'll look it up in the mean time anyways! Thanks Everyone! :)

 

[mishrashubham]

All right here are two freely accessible studies on TAMs. One on our favourite S.Cerevisiae and one on S.Enterica

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC416428/
http://nar.oxfordjournals.org/content/31/15/4517.full

 

[That Neuron]

Thanks Mishrashubham, I read them... They are very cool!

But as for my theory, I think there are to many "what ifs" for it to be applied to most organisms, and even if it is, it probably has little effect in their actual evolution... So time to let this one rest :(

 

[mishrashubham]

...it probably has little effect in their actual evolution...

I wouldn't say that; you never know, what seems trivial now, might turn out to be significant later on.

 

[That Neuron]

I wouldn't say that; you never know, what seems trivial now, might turn out to be significant later on.

I guess we will have to wait and see, If it doesn't... no one will know... But if it does, remember I thought of it first! Hahahaahaha

A quote I heard once kind of sums it all up

"The hardest thing for humans to understand is how much they don't understand" -Anonymous

 

[mishrashubham]

...But if it does, remember I thought of it first! Hahahaahaha

It has already been thought about. In fact, I stumbled upon TAMs while reading a paper on starvation induced mutations in certain bacteria.

 

[That Neuron]

It has already been thought about. In fact, I stumbled upon TAMs while reading a paper on starvation induced mutations in certain bacteria.

Oh no :( I thought I had searched everywhere, too bad :( Was it the same process? as in studying the rate of mutations, as opposed to the types of mutations?

Well not life devastating... I will survive. :D