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Author Topic:   Are mutations truly random or are they guided?
AZPaul3
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Posts: 4781
From: Phoenix
Joined: 11-06-2006
Member Rating: 4.9


Message 46 of 134 (548755)
03-01-2010 3:50 PM
Reply to: Message 45 by slevesque
03-01-2010 3:25 PM


Re: Neutral mutations
I think you missed Coyote's point. He was not saying Sickle cell was slightly- or nearly- anything.

The same mutation can be both beneficial and deleterious in the same population at the same time.

The overall effect of the mutation is beneficial to the population in total. That is why it stays around.

Edited by AZPaul3, : explain.


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slevesque
Member (Idle past 2977 days)
Posts: 1456
Joined: 05-14-2009


Message 47 of 134 (548756)
03-01-2010 4:01 PM
Reply to: Message 46 by AZPaul3
03-01-2010 3:50 PM


Re: Neutral mutations
If he didn't consider sickle cell to be slightly - or nearly - anything, then why did he quote me when I was referring to those type of mutations ??

Or I'm missing something ?


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Wounded King
Member (Idle past 2432 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 48 of 134 (548758)
03-01-2010 4:17 PM
Reply to: Message 42 by slevesque
03-01-2010 3:09 PM


Re: Neutral mutations
And also since the vast majority of mutations are only slightly deleterious

This has of course long been the received wisdom, but there is actually some doubt as to whether it actually holds up. There is experimental evolution research on mutation accumulation which suggests that in fact the rate of slightly deleterious mutations is only around 10% of all mutations and that most mutational load is caused by larger effect mutations which are much more easily removed by selection (Eyre-Walker et al., 2002). Looking at almost any paper with Adam Eyre-Walker or Peter Keightley on will reveal interesting research into the natural and frequency of deleterious and beneficial mutations.

TTFN,

WK


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Coyote
Member (Idle past 443 days)
Posts: 6117
Joined: 01-12-2008


Message 49 of 134 (548759)
03-01-2010 4:18 PM
Reply to: Message 47 by slevesque
03-01-2010 4:01 PM


Re: Neutral mutations
If he didn't consider sickle cell to be slightly - or nearly - anything, then why did he quote me when I was referring to those type of mutations ??

Or I'm missing something ?


I quoted you in order to provide a context for my comments. That way other posters don't have to search upthread to see what I was responding to.

And sickle cell anemia ranges from very deleterious to slightly deleterious, but in the presence of malaria it can be beneficial. The same mutation reacts differently depending on circumstances (whether reinforced or not) and the environment.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

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slevesque
Member (Idle past 2977 days)
Posts: 1456
Joined: 05-14-2009


Message 50 of 134 (548762)
03-01-2010 4:23 PM
Reply to: Message 49 by Coyote
03-01-2010 4:18 PM


Re: Neutral mutations
Ok, so sickle cell has no visible effect on the individual, but when in presence of malaria it has a visible effect which is beneficial ?

Because I thought the effect of sickle cell anemia was perceivable.


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Coyote
Member (Idle past 443 days)
Posts: 6117
Joined: 01-12-2008


Message 51 of 134 (548764)
03-01-2010 4:33 PM
Reply to: Message 50 by slevesque
03-01-2010 4:23 PM


Re: Neutral mutations
Because I thought the effect of sickle cell anemia was perceivable.

When reinforced it can be fatal. I'd call that perceivable.

I'm not sure what you are getting at?


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

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AZPaul3
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Posts: 4781
From: Phoenix
Joined: 11-06-2006
Member Rating: 4.9


Message 52 of 134 (548766)
03-01-2010 4:36 PM
Reply to: Message 42 by slevesque
03-01-2010 3:09 PM


Re: Neutral mutations
And also since the vast majority of mutations are only slightly deleterious, therefore 'undetected' by natural selection won't become beneficial in a changing environment (since the environment is a component of natural selection) and so will stay deleterious.

This also is not correct, slevesque.

A trait (mutation) labeled neutral in the present environment may not be so in a changed environment. The trait may not be subject to strong selection pressures in the present environment but change the environment and the selection pressures change as well.

Environments are always changing, though generally not on a scale less than millennia, and that is why genetic diversity is important to a species survival. As the environment changes those individuals with some neutral or slightly bad traits (as viewed in the old environment) may be better adapted to the new.


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slevesque
Member (Idle past 2977 days)
Posts: 1456
Joined: 05-14-2009


Message 53 of 134 (548767)
03-01-2010 4:40 PM
Reply to: Message 48 by Wounded King
03-01-2010 4:17 PM


Re: Neutral mutations
Thiswould mean that of all the mutations I have from my parents, only 10% are slightly deleterious and the rest are detectable by selection ?

First, doesn't this destroy Kimura's theory of molecular evolution (since it relies on the fact that the vast majority of mutations are nearly-neutral) ?

Second, If we only take the example of the 175 point mutations. that means roughly 18 are not subject to natural selection. That leaves about 157 of those mutations that will be visible by natural selection. There are more deleterious mutations then beneficial, and even with a very favorable ratio of 3:1 it gives us about 118 deleterious mutations and 39 beneficial ones. All in the same individual. How will natural selection ever sort them. How will it filter out those deleterious mutations ?

And this is a look at the point mutations, nevermind the other types. In light of this, I think the fact that in reality I am about selectively just as fit as my father in the present environment is showing that the majority of mutations must be nearly-neutral, as Kimura figured out I guess.


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slevesque
Member (Idle past 2977 days)
Posts: 1456
Joined: 05-14-2009


Message 54 of 134 (548768)
03-01-2010 4:43 PM
Reply to: Message 51 by Coyote
03-01-2010 4:33 PM


Re: Neutral mutations
Well slightly deleterious mutations are by definition unperceivable by natural selection, and so if sickle cell anemia can be detected by NS than it doesn't fall into that category.

And well, if it doesn't fall into that category than I'm not sure where you are getting at since I agree that some mutations can be termed beneficial or deleterious depending on the environment as your examples shows pretty clearly. I was just saying that this doesn't apply to all mutations.


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AZPaul3
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Posts: 4781
From: Phoenix
Joined: 11-06-2006
Member Rating: 4.9


Message 55 of 134 (548769)
03-01-2010 4:43 PM
Reply to: Message 50 by slevesque
03-01-2010 4:23 PM


Re: Neutral mutations
A person with the one sickle cell gene from one parent is better protected from malaria. Since we inherit copies of genes in pairs, one from mom, one from dad, in those instances where an individual inherits a sickle gene from both the result is devastating to the individual. That results in the sickle cell disease. The remainder of the population with only one copy of the gene receives a benefit.

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slevesque
Member (Idle past 2977 days)
Posts: 1456
Joined: 05-14-2009


Message 56 of 134 (548770)
03-01-2010 4:45 PM
Reply to: Message 52 by AZPaul3
03-01-2010 4:36 PM


Re: Neutral mutations
A nearly-neutral mutations by it's very definition is one who has no perceivable effect by NS. This includes selective pressures in any environment.

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Taq
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Posts: 8207
Joined: 03-06-2009
Member Rating: 3.9


Message 57 of 134 (548773)
03-01-2010 4:48 PM
Reply to: Message 11 by Bolder-dash
02-28-2010 10:20 PM


Once again you and Perry and others are trying to run away from the random aspect of the entire ToE, as if natural selection all by itself can do anything. The fact that you can neither adequately demonstrate the accuracy of either the random mutations aspect of it, nor the natural selection aspect of it, does not prevent you from claiming that the random mutations part is a "very small part of it."

There is an easy test for this. Compare two genomes, say the human and chimp genome. What you will find is that synonymous mutations (mutations which do not change the amino acid sequence) outnumber non-synonymous mutations. You can also compare the rate of change between exons and introns which again relates to protein function and stabilizing selection. Another source to test is the LTR's of ERV's. When an ERV inserts the flanking LTR's are identical. Over time these will diverge as different mutations accumulates in each LTR. What one should see is divergence over time, and that is exactly what is seen.

Both the randomness of mutations and natural selection in the past can be tested for, and has been tested for.


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AZPaul3
Member
Posts: 4781
From: Phoenix
Joined: 11-06-2006
Member Rating: 4.9


Message 58 of 134 (548774)
03-01-2010 4:54 PM
Reply to: Message 56 by slevesque
03-01-2010 4:45 PM


Re: Neutral mutations
I'm afraid that is not correct. Selection pressures result from the attributes of the environment. Change the environment and you have, by definition, changed its attributes thus its selection pressures.

Don't think of Natural Selection as some monolithic entity separate from the environment. The attributes of the environment, the selection pressures presented by the environment, are Natural Selection. Change the environment, change the selection pressures, change NS.

Edited by AZPaul3, : No reason given.

Edited by AZPaul3, : No reason given.


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slevesque
Member (Idle past 2977 days)
Posts: 1456
Joined: 05-14-2009


Message 59 of 134 (548776)
03-01-2010 6:36 PM
Reply to: Message 58 by AZPaul3
03-01-2010 4:54 PM


Re: Neutral mutations
I understand Natural selection. But you don't seem to see that many mutations are so subtle that it doesn't have any noticeable effect on the phenotype. In other words, the same person with or without the mutation the difference is almost nile.

It's like if you were on top of a tower of pillows, and asked you to detect an object under it. Sure sometimes it's a bowolign ball, but the majority of times it's a simple grain of rice you won,t detect.


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Dr Adequate
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Posts: 16107
Joined: 07-20-2006
Member Rating: 8.3


Message 60 of 134 (548777)
03-01-2010 6:44 PM
Reply to: Message 59 by slevesque
03-01-2010 6:36 PM


Re: Neutral mutations
I understand Natural selection. But you don't seem to see that many mutations are so subtle that it doesn't have any noticeable effect on the phenotype.

But somehow can be proclaimed "deleterious" even though their effect is unmeasurable.


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