Are mutations truly random or are they guided?

You speak french ?

Okok, Yeah I'm from quebec so my original language is french and so your finishing line kind of surprised me since I'm the only one here who speaks french that I know of.

I'll add another point that hasn't been highlighted. If the cell had a mechanism to provoke the mutations it needed, that would help it along it's evolution (asI understood the OP) then this very same mechanism would have had to have evolved. and since it wasn't there to direct it's own happening, classical evolution with random mutation are what made this mechanism in the first place.So even if random mutations appear to you that they can't make biological systems grow in complexity, adding a mechanism to make them none-random doesn't take those random mutations out of the whole picture.

I agree with what you said, but of course this does not apply to all mutations. Many Mutational diseases won't help you whatever the environment.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.

Sickle cell anemia isn't a slightly deleterious mutation. (or nearly-neutral mutation. however you want to call them)Because by definition they aren't perceived by natural selection. In other words, if their deleterious or beneficial nature is dictated by the environment (ie the selection pressures) then they are not slightly deleterious 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 ?

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.

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.

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.

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.

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.

I'll start a topic on this later on this week about all this. The reason being that I don't have the references I need to support what my memory seems to remember (mutation rates, deleterious ratios, etc.)But I will give a brief answer to your beetle example, even though the explanation will be similar to the ones coyote gave.A beetle changing color isn't a near-neutral mutation, precisely because it gives a noticeable advantage to the beetle in a given environment. The mutation caused a change that has a sufficient enough impact on the phenotype for this (it changed color).But as I said, I'll come back on this. I don't have Dr. Sanford's book with me right now.PS On a final note, only 3% of the human genome codes for genes. But of course, what the ENCODE project is showing us is that more then 100% of it is being transcripted (because sometimes in both directions). This does not prove that it all serves a function of course, but it is very indicative of that in my opinion. Why would the cell spend so much energy and ressources transcripting what it doesn't even use ? It would make no sense in my opinion. I could make the prediction that eventually, science will find a function for all of the genome and that therefore, no mutation is actually effectively neutral.

He is saying that the entire genome is being coded because the RNA transcriptases aren't specific enough to the gene-coding regions, and so mistakenly transcript other regions which they shouldn't.Which as good a guess as any, but I prefer thinking that maybe the genome is even more complex then we thought Edited by slevesque, : No reason given.