Proving Darwin's theory

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genovese
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Proving Darwin's theory

Post by genovese » Mon Jan 21, 2008 3:33 pm

I read that there have been over 3000 different mutants produced in Drosophila melanogaster. Has anyone tried to place one of these mutants into a particular environment where they might fare better than in a normal environment. Having thus produced a variant of the species it could then be kept isolated in this false environment for many generations to see if eventually it had lost the ability to reproduce with the original Drosophila melanogaster. A new fly species would then have been produced confirming the modern view of Darwin’s theory on speciation? :roll:

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Post by mcar » Tue Jan 22, 2008 1:18 pm

Well as I have read about geographical barriers, if these new variants will be kept isolated with the original D. melanogaster. that will be adequate to say that new species are formed. However, it is also said that natural selection as a mean to form new species must have been processing over a long period of time. Mutations can happen abruptly and the effects on their variants are more likely negative and the less chance of suriving the normal environment.
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Post by genovese » Tue Jan 22, 2008 2:40 pm

mcar wrote:Well as I have read about geographical barriers, if these new variants will be kept isolated with the original D. melanogaster. that will be adequate to say that new species are formed. However, it is also said that natural selection as a mean to form new species must have been processing over a long period of time. Mutations can happen abruptly and the effects on their variants are more likely negative and the less chance of suriving the normal environment.


Yes I realise all of this. I was hoping that out of the 3000 mutants or so someone could find one variation that would work better with a particular environment not normally found for this species. This artificial environmnet could then be maintained or developed further for the mutant strain to remain isolated from the parent strain. ie put some environmental pressure to further select out other variations within the mutant to improve its survival still further.Now this may take millions of generations but this could be done in some National laboratory perhaps with several generations of scientists, until a new species of fly had developed. Darwin could then rest in peace.

After all NASA sent out a deep space probe to communicate with other life forms and no one is expecting a response in our generation.

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Post by canalon » Tue Jan 22, 2008 3:07 pm

Well some similar work has been started with bacteria (see work by R.Lenski et al). And although bacterial species are harder to define than for multicellular organisms, they showed that speciation was indeeed occuring in populations propagated for thousands of generation. See here:
http://www.pnas.org/cgi/content/abstract/96/13/7348
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Post by genovese » Tue Jan 22, 2008 6:27 pm

Thanks canalon, that is really very interesting. I thought it would be harder to prove in bacteria than in multi-cell organisms. I imagined that bacteria could always pass genetic material between themselves .

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Post by alextemplet » Tue Jan 22, 2008 7:30 pm

It would be best to carry out such experiments with organisms that have short life spans so that the rate of evolution would be accelerated and it would thus be easier to see the results sooner.
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Post by genovese » Tue Jan 22, 2008 8:31 pm

Yes I agree Alex. I thought of the fruit fly because because we seem to know a lot about how to get mutants from this little creature and although they don't reproduce as quickly as bacteria they do have a reasonably fast life cycles and are multicellular. Darwin's observations were done on multicellular organisms.

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Post by alextemplet » Thu Jan 24, 2008 1:14 am

If I remember correctly, doesn't the fruit fly have only eight chromosomes? I read once that this is why it is used so often in genetic research, because the simpler code makes it easy to understand and manipulate.
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Post by mcar » Thu Jan 24, 2008 11:50 am

And really if this fruitfly is to be subjected to artificial factors where we would like to see how Darwin's thoughts work. My colleague talked about the brontosaurus principle, there's the time that a bigger organism has of great advantage but as time goes by, the least one can always take also of the advantage after some time. And since of very simple genetic material, modification can easily do its work on the organism.
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Post by MrMistery » Thu Jan 24, 2008 12:43 pm

the fruit fly is used for many reasons: short generation time and the existence of polytene chromosomes in its salivary glands are the two most important. Those chromosomes are giant: formed from more than 2000 copies of the chromosome if i remember correctly. Thus it makes them easy to observe the chromosomes.
2n=8 is not very small... Heck, there is an Ascaris with 2n=2
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Post by alextemplet » Wed Jan 30, 2008 6:04 pm

2n=8 is a lot smaller than some other organisms.
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Post by MrMistery » Wed Jan 30, 2008 7:47 pm

sure it is... there's a fern with 2n=1246(or something like that). But while I agree the small number of chromosomes was a factor in picking Drosophila it was not the decisive one. The decisive one was that the polytene chromosomes were easy to observe even with the microscopes available back in Morgan's time. Now modern techniques can identify genes on chromosomes with no difficulty, but of course people stick with that organism that we know sooooooooo much about.
Oh, another important factor was the fact that the fruit fly has over 500 natural mutants.
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