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The Long Term Evolution Experiment ( Ltee )


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#81 Guest_shpongle_*

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Posted 29 November 2008 - 09:47 AM

No your not.You "they" are getting their knowledge from circular reasoning,based on the assumption that our genes were identical to chimps.You cant hide half of the problem in a hypothetical ancestor.

I may be wrong,but that sounds like what you are doing.

Thanks.

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I think you are misunderstanding this. It has nothing to do with "hiding half the problem in a hypothetical ancestor". It's more like basis statistics.

If you have two diverging populations that share a common ancestor, assuming the rate of divergence is about equal in both lineages (i.e. the mutation rate is the same), the net divergence between both populations will be approximately double the divergence in each population from the ancentral population. IOW, lineage A will accumulate a certain number of mutations and lineage B will also accumulate a certain number of mutations. If the mutations are strictly random, the overall divergence will be the mutations in A + the mutations in B, that make up the overall difference between A and B.*

The only assumption in this is the rate of divergence in each lineage, not that they shared an ancestor. What we are trying to see (which I've already shown repeatedly) is that relative rates of mutation are enough to account for those differences if they did share a common ancestor.

* Obviously there will likely be some overlap between populations, which is why the overall differences are logarithmic based on genome size vs time. But over a 5 million year period, it's pretty close to linear.

#82 jason777

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Posted 29 November 2008 - 11:20 AM

Thanks,

I think i see what your saying now.

#83 deadlock

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Posted 07 December 2008 - 03:00 AM

No.  You're dividing by f as well, so it's just 130.
*shrug*  I'm getting my knowledge from a textbook on the subject.  I can give you direct references if you'd like.

Of course, if you are going to counter this you might want to explain why you think so, instead of just resorting to "yes/no" responses.

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This leads to a further rather neat result. Let μ be the rate at which neutral mutations occur, given as probability of mutation per nucleotide per generation. Then there will be μfNe mutations per site per generation in the population

Genetic Drift

f gives the ploidy of the specie, so it´s equal 2.
Ne is the populations size.So, if we want to know the number of mutations per individual, Ne is equal 1.

But we already know that the number of mutations per individual is 130.

So, μ * 2 * 1 = 130. μ = 130 / 2. μ = 65.

65 is the number of mutations expected to get fixed per generation.But it does not mean it will get fixed in the generation it happened.It will take a long time for them get fixed.

You cannot multiply 65 * 250,000 = 16,250,000 mutations fixed per lineage.

The rate of substitution is equal to the rate of mutation, although it is quite different from the rate of fixation. A great error was introduced into comparative studies of taxa in estimating the rate at which alleles or bases were and remain fixated and assuming that rate to be the substitution rate

Misconceptions and false expectations in neutral evolution

In a finite population, a mutant gene is either fixed in the population or lost
from it within a finite length of time. A theory was presented which enables us
to obtain the average number of generations until fixation, and separately, that
until loss, based on the method of diffusion equations. Also, Monte Carlo experiments were performed to test some of the theoretical results.-It was shown that a single mutant gene, if it is selectively neutral, takes about 4Ne, generations until fixation in a population of effective size Ne.


THE AVERAGE NUMBER OF GENERATIONS UNTIL FIXATION ( MOT00 KIMURA AND TOMOKO OHTA, )

So, for a population of 100,000 individuals, it will take 4 * 100,000 generations until the mutations from the first generation get fixed in the population.

#84 CTD

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Posted 06 March 2009 - 06:28 PM

tharock220 has provided a couple more links on the LTEE:

http://www.newscient...in-the-lab.html

and

http://myxo.css.msu....i/summdata.html

#85 deadlock

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Posted 07 March 2009 - 01:49 PM

tharock220 has provided a couple more links on the LTEE:

http://www.newscient...in-the-lab.html

and

http://myxo.css.msu....i/summdata.html

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Nothing new

#86 AFJ

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Posted 15 August 2009 - 12:24 PM

The Long Term Evolution Experiment (LTEE) has been going on since 1988, and its goal was to study how related mutations can accumulate.They used Escherichia Coli because it can metabolize citrate internally during aerobic growth on other substrates.The only known barrier to aerobic growth on citrate is its inability to transport citrate under oxic conditions.Indeed , atypical E.Coli that grow aerobically on citrate have been isolated from agricultural and clinical settings, and were found to harbor plasmids, presumably acquired from other species, that encode citrate transporters.So, the ability to digest citrate depends on related  mutations.
They started out with 12 individual, identical E.Coli bacteria making 12 colonies.They fed them glucose and citrate, and gave them 12.2 times more citrate than glucose.The expectation was that if the E.Coli did evolve into a form that could digest citrate, that new variety would flourish in the citrate -rich environment and drive the old variation to extinction.
So, it took more than 30.000 generations to fully evolve a capability that was already almost there, and it only happened in 1 out of 12 populations.In human terms 30.000 generations is 600.000 years.The scientists don´t know how many mutations are related to the trait yet, but let´s imagine that were 1000 mutations.So, we had 1000 beneficial mutations accumulated in 30.000 geneations.The difference between human and chimps genetic code is 4%, 120 millions of mutations. The numbers of generations necessary to accumulate 120 millions of mutations woul be : ( ( 120 * 10^6 ) / 10^3 ) * 30 * 10^3 = 36 * 10^8 generations.In years terms it would be : 36 * 10^8 * 20 = 72 billions of years.

Science Against Evolution

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Thanks deadlock,

In my reading of this experiment I found a paper that stated there was also physiological trade-offs as well as ecological specialization of the colonies. This is known as antagonistic pleiotropy--

"Antagonistic Pleiotropy is when one gene controls for more than one trait where at least one of these traits is beneficial to the organism's fitness and at least one is detrimental to the organism's fitness ." wikipedia

Not to mention the fact that comparing bacteria to all other organisms is irrelevant. What else consumes plasmids which change our DNA? Along with viruses.




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