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Percentage of Beneficial/Deleterious mutations

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Percentage of Beneficial/Deleterious mutations

Postby ryangrannell » Mon Oct 18, 2010 5:53 pm

Hello.
I wasn't too sure if I should post this in evolution, genetics or molecular biology, hopefully this is a good fit.

I'm currently playing around with an interesting mathematical model involving DNA Polymerase III in E. Coli, and I need to determine the percentage of mutations that are deleterious, beneficial and weakly deleterious/beneficial.

According to Wikipedia, 70% of mutations (on genes) are deleterious, and the remainder are neutral/beneficial. I know that genetic drift would make it difficult to obtain an exact figure for the neutral (or nearly neutral) mutations, but I imagine the percentage of beneficial mutations is easy to determine. What is the value for beneficial mutations to genes. Even an educated guess would be appreciated :)

Oh, and if anyone knows the values for beneficial/neutral/harmful mutations on non-coding detail, I would really appreciate it :D

Thanks
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Postby canalon » Mon Oct 18, 2010 7:52 pm

I honestly don't know how anyone can calculate such numbers. Mutations that would be deleterious in one environment might be highly advantageous in another (ex: streptomycin dependance in many bacteria, and E. coli in particular).
And even if one environment was given, to asses all the muattaions, you would have to test every mutation against the other in the same defined challenge. I can only see the fully lethal mutations being easy to identify.

Add to that the problem of definition of mutation: point mutations? insertions/deletions? of how many nucleotides? so I guess it is more complicated than what you seem to estimate, and I doubt that any number would be more than an educated best on a rough average.
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Postby ryangrannell » Mon Oct 18, 2010 9:32 pm

Ah, so there probably isn't any official number. I remember hearing about an experiment in which E. Coli was placed in some medium containing a particular sugar, and the E. Coli eventually evolved a new chemical pathway to metabolise it, so perhaps that experiment might yield a rough indicator of the %positive mutations...I don't know the rate of insertions/deletions, and my figures only account for snp's, but hopefully I can get some semi-meaningful results for my mathematical model. Thanks for the reply, I probably would have wasted hours trying to google the figures otherwise.
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Postby Julie5 » Tue Oct 19, 2010 10:17 am

From what little I understand about it (!), the Aids virus finds it highly advantageous to it to be extremely mutable, because it keeps out-mutating all the patients's immune system's and drug regimes efforts to kill it! So much so that I believe one line of treatment research is to actually increase the rate of mutation within the virus so much, that it starts to impact its own survivability, and dies instead.

In cancers, I believe the rough figure for the number of mutations (eg, in mitosis checkpoint genes etc) that tip the cell into malignant transformation is between six and ten, so presumably that is the maximum tolerable number of deleterious mutations (in those growth-regulatory genes)?
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Postby JackBean » Mon Nov 01, 2010 7:56 am

yeah, but I guess it's advantage for AIDS, because it has so many "offspring", that if some dies due to bad mutations, it won't much matter, because there will be plenty of others ;) And as said canalon, in one enviroment can be mutation beneficial, while in other harmfull and that's the reason, why is it so beneficial for AIDS to keep high mutual rate, because we are trying so many things all the time again and again ;)
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