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jaimehlers



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Most mutations have a negative effect (often lethal), some are neutral, and a tiny few improve adaptation (or sexiness in some cases).
You never did get around to showing the evidence to support your assertion that most mutations have negative effects (either harmful or lethal).  Given that the discussion with DT went off the rails around that time, this isn't surprising.  So I figure this topic might be better for continuing that discussion.

What you showed is that people in Ukraine, after the Chernobyl disaster, have an unsustainably high rate of lethal and harmful mutations - which, given the natural population decrease there, argues against the number of lethal mutations being anywhere near as high in a healthy population of humans.  Indeed, your statement above is almost a direct quote of the typical creationist argument regarding mutations.  "Most all mutations are detrimental, a few are neutral, and extremely few if any are clearly beneficial."

Now, the mere fact that creationists repeat an argument does not make it wrong.  What makes it wrong is that the argument for a high number of deleterious mutations is not supported by actual scientific studies regarding genetic mutations.

http://www.genetics.org/content/156/1/297.full - "The average mutation rate was estimated to be ~2.5 × 10?8 mutations per nucleotide site or 175 mutations per diploid genome per generation" and "Using conservative calculations of the proportion of the genome subject to purifying selection, we estimate that the genomic deleterious mutation rate (U) is at least 3."  Now, granted, they are using a conservative estimate, which means it could be (and likely is) higher, but...3/175 is less than 2%.  Tripling that rate for the sake of argument results in a 5% rate of deleterious mutations, which is not nearly high enough to justify your (or creationists') argument that most mutations have a negative effect.

http://www.webpages.uidaho.edu/newton/math501/fa2007/adaptivemutrate_science07.pdf - "Given the estimates for the overall mutation rate in E. coli (30) and its genomic deleterious
mutation rate (1), our estimate of Ua implies that 1 in 150 newly arising mutations is beneficial and that 1 in 10 fitness-affecting mutations increases the fitness of the individual carrying it."  What this says is that the rate of deleterious mutations in E.coli is 1/30, and the rate of beneficial mutations is 1/150, which accounts for 6/150 mutations.  The rest, therefore, must be neutral.

The implications are clear.  The mutation rate follows a bell curve[1] rather than an asymptomatic one[2], at least under normal circumstances on Earth (meaning, there are no environmental factors which push the mutation rate up).  Furthermore, even if the mutation rate is increased due to environmental factors (such as the ones that hold in Ukraine, today), there is no reason to expect that the proportion of beneficial/neutral/deleterious mutations would change - only the total mutation rate.  This still leads to a higher number of deleterious mutations, and since a single lethal mutation overrides all other mutations in terms of viability...

By the way, I do understand the point you were trying to make about lethal mutations removing themselves from the gene pool.  The problem is that new mutations always crop up, in every generation, and some of those will be lethal.  While it's certainly true that lethal mutations aren't conserved, that means nothing as far as new lethal mutations are concerned, and all it takes is one.  My point is that you shouldn't conclude that since lethal mutations aren't conserved, then it doesn't matter how many there are.  Because as you showed with the post-Chernobyl Ukranians, a high enough number of lethal mutations threatens the long-term survival of a species.
 1. a low number of deleterious mutations, a high number of neutral mutations, and a low number of beneficial mutations
 2. a high number of deleterious mutations, a moderate/low number of neutral mutations, and a low number of beneficial mutations
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Graybeard Well worth posting November 19, 2013, 03:41:12 PM