lost advantageous alleles?

[dichotomy]

I’d still assume the ‘lost’ advantageous alleles would have been lost for an environmental reason; it wouldn’t be just through chance only.

I’d even consider that the alleles loss was a kind of ‘spreading of risk’ in biological terms (Is there a biological term for ‘spreading risk’?). Say if you had a red flower' date=' Blue flower and white flower of the same species. Red might be the only survivor in that group at a moment in time, but depending on how the environment may have changed, white or blue may have been more successful. Thus, the advantage is the variety within the species? [/quote']

 

No, the allele can be lost simply through chance. This is much more likely to happen in small populations of course, but it can happen that the dice fell in such a way that none of the offspring of the next generation received that particular allele, and so it is lost from the population. Of course alleles can be lost environmentally, but they can be lost this way also, and through a random mutation that renders the gene non-functional, or through a natural disaster that kills all the individuals with that one allele, etc.

 

This was something from a previous thread. I was surprised to learn that advantageous alleles can sometimes be lost without apparent environmental reason.

So, what are some of the better examples of advantageous alleles that have been lost through chance, that is, without apparent environmental cause?

[CDarwin]

The process is called genetic drift, and it happens all the time. Consider a hunting party of Homo habilis that consists of the best hunters in the whole population. If they go out and a rock falls on them, those advantageous huting alleles are lost for no better reason than the fact that their skulls weren't rock-proof.

[vampares]

There is also the potential to loose or effectively loose the benefits of advantageous recessive traits by diffusion. There was an issue of Time magazine that had a composite of what "mixed" America would look like. That is if everyone in America were to reproduce without reservation. If this were the case, the recessive traits would be rapidly drowned out.

 

Maybe someone knows the equation for calculating the homozygous expression of a gene in a given gene pool.

 

If it is so unlikely it can no longer be selected for, it becomes, in effect, worthless. Institutionalized inbreeding would isolate it from an inequitable gene pool and give it opportunity for expression (as well as preservation and the extractive differentiation of genotype).

 

Of course the majority of reproduction is done with bias towards race and other criteria. If and when it is not the resulting offspring is usually associated with an ethnicity regardless. This has the potential advantage of adding traits to a "race", or otherwise homogeneously closed gene pool. The selection of the traits from the next generation of "in-mixed" offspring is then possible. To select recessive traits, the offspring must be "hybrid-mixed" and require more offspring for the observation of the recessive trait.

 

Due to the complex constraints of such reproduction it is rare except in the offspring of war parties. For example (pure) blue-eyes is extremely rare in the African and Asian populations. We can therefore safely assume that Caucasians have not substantially (or overwhelmingly at least) contributed to to these gene pools as some of the Vietnam horror stories might suggest.

 

The Austrialian population is an interesting one. They have, over several generations, homogenized what was a select group of individuals. Interestingly these homogenized populations exhibit their multiple origins better than those of the founders and shows a selectivity with regard alleles in combination. It is distinct none the less.

 

The American population on the otherhand, a less uniformly installed population, tends to display disunion more readily and is not has not been pruned selectively in regards one to the other.

 

We can thereby assume that the Australian population did slough off some alleles to accommodate the others in order to achieve harmony.

[SkepticLance]

A good example of an advantageous allele that has been lost is the crucial one in the Vitamin C manufacturing process inside the body of Homo sapiens.

 

A large number of mammals can make their own vitamin C. We cannot. We must get it in our food. Yet we have most of the genetic apparatus for making the stuff. One crucial gene has been lost. This probably happened during a time when our pre-human ancestors ate a lot of fruit. The change would not have been of any consequence then, and the crucial gene was lost.

[vampares]

Hmm, I wonder where that gene would be. Maybe there is evidence remaining of what happened to it.

[dichotomy]

The process is called genetic drift, and it happens all the time. Consider a hunting party of Homo habilis that consists of the best hunters in the whole population. If they go out and a rock falls on them, those advantageous huting alleles are lost for no better reason than the fact that their skulls weren't rock-proof.

 

 

Rock falls are still an obvious environmental cause. The 'chance' that Paralith seems to refer to is a random mutation without environmental cause, and without benefit. A rockfall would at least serve the purpose to any survivor, or witness, that rock fall can occur and should be considered something to stay clear of when practical. Hence strengthening the knowledge of those with the surviving allelles.

[SkepticLance]

One of the factors leading to loss of advantageous alleles is small population. If the species has a very large population, then any 'accident' that causes a loss will be compensated for by the fact that numerous other individuals carry the advantageous allele.

 

However, if the species concerned has a very small number of individuals, then a 'rock fall' type accident is enough to remove an allele from the population.

 

Homo sapiens, in spite of our large numbers, is a genetically non diverse species. Variation from any one individual to another is only about 0.1% genetically. Many paleoanthropologists believe that there was a time when our forebears consisted of a very tiny number of individuals, and all of us today are descended from that small number. Hence our current lack of diversity.

 

That situation, of course, is rife for loss of alleles through random chance.

[dichotomy]

A good example of an advantageous allele that has been lost is the crucial one in the Vitamin C manufacturing process inside the body of Homo sapiens.

 

A large number of mammals can make their own vitamin C. We cannot. We must get it in our food. Yet we have most of the genetic apparatus for making the stuff. One crucial gene has been lost. This probably happened during a time when our pre-human ancestors ate a lot of fruit. The change would not have been of any consequence then, and the crucial gene was lost.

 

This is more like what I was looking for. But even here we see an environmental reason for the supposed ‘advantageous’ gene loss, i.e. there was no shortage of Vit C. in our diets due to the widespread availability of fruits and veg. And still to this day there is no shortage, to the bulk of humanity, of Vit C. food sources. So, the advantage was not an advantage in this scenario. And, perhaps there may have been a strong disadvantage in those that did self make Vit C, hence the loss?

 

One of the factors leading to loss of advantageous alleles is small population. If the species has a very large population, then any 'accident' that causes a loss will be compensated for by the fact that numerous other individuals carry the advantageous allele.

 

However, if the species concerned has a very small number of individuals, then a 'rock fall' type accident is enough to remove an allele from the population.

 

A small population with small global distribution is generally not an advantageous gene pool any way, because of the fact that it is small, poorly distributed and vulnerable to rock falls. So, if this population is affected via a ‘rock fall’ type incident, it would either serve to strengthen the remaining population, or cause extinction, giving other species advantage. Isn’t this how all species either retain advantageous genes and evolve, or become extinct? I.e. through a series of environmental causes that cause ‘seemingly’ random, but not really random, gene mutations. The mutations are driven by the environment.

 

It seems that what is really advantageous are the genes in a species as a whole, and not the advantageous ones in the odd exceptional individual here and there?

[CDarwin]

A small population with small global distribution is generally not an advantageous gene pool any way, because of the fact that it is small, poorly distributed and vulnerable to rock falls. [/Quote]

 

I don't think you can have an "advantageous gene pool" of the sort that's going to be acted on by selection.

 

So, if this population is affected via a ‘rock fall’ type incident, it would either serve to strengthen the remaining population, or cause extinction, giving other species advantage. Isn’t this how all species either retain advantageous genes and evolve, or become extinct? I.e. through a series of environmental causes that cause ‘seemingly’ random, but not really random, gene mutations.

 

But the environment isn't always being selective. Sometimes, a rock just falls on your head. It doesn't matter how smart, or fast, or good a hunter you are. I don't understand what you mean by this "strengthening" the remaining population. There's no selection here. The rock would have to just randomly fall on someone with disadvantageous alleles.

 

The mutations are driven by the environment.[/Quote]

 

Only in an environment of radiation. Mutations aren't driven by the environment, they are selected by it.

 

It seems that what is really advantageous are the genes in a species as a whole, and not the advantageous ones in the odd exceptional individual here and there?

 

This seems like an obvious statement, but individuals have genes, not species. So if you wipe out an individual, then you wipe out that individuals genes. If an allele is sufficiently rare enough, then when you wipe out the individual the whole species looses the allele, advantageous or not. That's the only answer I know to give you.

 

Rock falls are still an obvious environmental cause. The 'chance' that Paralith seems to refer to is a random mutation without environmental cause, and without benefit. A rockfall would at least serve the purpose to any survivor, or witness, that rock fall can occur and should be considered something to stay clear of when practical. Hence strengthening the knowledge of those with the surviving allelles.

 

You're missing the point. Genetic drift is the "random" elimination of alleles without any selective environmental cause. The rock fall is just an example, and your exception is only valid in a limited number of circumstances: i.e. when a member of the same species is present as a witness and is capable of understanding and learning from the situation.

 

If your just asking about neutral mutations... yeah. Most mutations are neutral. You were born with around 20 mutations, all but 5 of which were on non-coding regions.

 

You seem to be thinking in terms of the environment "causing" mutations. The environment causes the selection of mutations, not the mutations themselves.

[dichotomy]

I don't think you can have an "advantageous gene pool" of the sort that's going to be acted on by selection.

 

I’m not sure I understand. We are not just talking ‘selection’. There is the ‘chance’ question too. Either way small populations are a disadvantage until they can get larger. I’d think a successful species, initially, need a challenging, unpredictable environment to trigger the development of advantageous genes.

 

But the environment isn't always being selective. Sometimes, a rock just falls on your head. It doesn't matter how smart, or fast, or good a hunter you are. I don't understand what you mean by this "strengthening" the remaining population. There's no selection here. The rock would have to just randomly fall on someone with disadvantageous alleles.

 

Strengthen the remaining populations collective knowledge. Thereby giving a future individual with exceptional alleles a better chance of survival.

 

 

Only in an environment of radiation. Mutations aren't driven by the environment, they are selected by it.

 

Ok, driven is the wrong term. Initially caused by, perhaps.

 

This seems like an obvious statement, but individuals have genes, not species. So if you wipe out an individual, then you wipe out that individuals genes. If an allele is sufficiently rare enough, then when you wipe out the individual the whole species looses the allele, advantageous or not. That's the only answer I know to give you.

 

Yes, but if the individual was so rare, he couldn’t have been that advantageous after all, could he? If the individual spread his genes about enough he would obviously have advantageous genes. Species share most of the 'true' advantageous genes, that’s why a species is successful or not, yes?

 

You're missing the point. Genetic drift is the "random" elimination of alleles without any selective environmental cause. The rock fall is just an example, and your exception is only valid in a limited number of circumstances: i.e. when a member of the same species is present as a witness and is capable of understanding and learning from the situation.

 

Yes, you can call it ‘random’, but it still has environmental causes/triggers preceding it. Therefore it’s not true randomness. If you are defining random in this way – i.e. rocks falling with physical causes that were unexpected by a group of men, then I can’t argue with your definition of what constitutes random/chance. If this is the evolutionary/biological definition of random, then that’s fine, I can understand it from this perspective. But what I observe is that everything has a root cause, be it physical, chemical or unidentified other. Just because it can't be seen, this does not mean it is not there. Chance has a cause.

 

Lets see if I understand these biological definitions – selective environmental causes are things like sexual attraction to a mate, fecundity. Random environmental causes are rock falls, lightening, natural disasters?

 

 

You seem to be thinking in terms of the environment "causing" mutations. The environment causes the selection of mutations, not the mutations themselves.

 

What I’m saying is that environment is the initiating trigger or cause of gene loss or mutation, whether its selection or chance.

 

cheers.

[iNow]

I’m not sure I understand. We are not just talking ‘selection’. There is the ‘chance’ question too. Either way small populations are a disadvantage until they can get larger.

Not necessarily. You are making too many assumptions. A smaller population is quite advantageous when there are limited resources in the environment. Too large a population and those resources get used too quickly and all of them die. That's just one counter example, but it's enough to prove your point incorrect.

 

 

I’d think a successful species, initially, need a challenging, unpredictable environment to trigger the development of advantageous genes.

What is the basis of this assumption?

 

 

Ok, driven is the wrong term. Initially caused by, perhaps.

It's the wrong idea, not the wrong term. Mutations have nothing to do with the environment. They are part of the genes and the combination of them. The environment just selects for certain mutations.

 

 

Yes, you can call it ‘random’, but it still has environmental causes/triggers preceding it. Therefore it’s not true randomness. If you are defining random in this way – i.e. rocks falling with physical causes that were unexpected by a group of men, then I can’t argue with your definition of what constitutes random/chance. If this is the evolutionary/biological definition of random, then that’s fine, I can understand it from this perspective. But what I observe is that everything has a root cause, be it physical, chemical or unidentified other. Just because it can't be seen, this does not mean it is not there. Chance has a cause.

Sounds a lot like intelligent design if you ask me. You make so many unsupported assumptions, and that is what is causing your confusion.

 

Lets see if I understand these biological definitions – selective environmental causes are things like sexual attraction to a mate, fecundity. Random environmental causes are rock falls, lightening, natural disasters?

To be clear, they are all selective. There is no need for distinction.

 

 

What I’m saying is that environment is the initiating trigger or cause of gene loss or mutation, whether its selection or chance.

 

It's not, though. The way the genes are passed and combined is the trigger for the mutation. The environment is simply the context in which those mutations are selected for or against.

[dichotomy]

Not necessarily. You are making too many assumptions. A smaller population is quite advantageous when there are limited resources in the environment. Too large a population and those resources get used too quickly and all of them die. That's just one counter example, but it's enough to prove your point incorrect.

 

Ok, point taken. A population needs to be of a ‘functional’ size for it's environment. But, small populations are still at a greater disadvantage, particularly if something as simple as a chance rock fall causes them catastrophe.

 

What is the basis of this assumption?

 

Why else would advantage evolve? It evolves from pressure, not lack of pressure. You avoid a collision with a truck because of pressure, not lack of pressure. Your genes then get a better opportunity to spread. The pressure of abundant leaves high up in trees causes giraffes to evolve the advantage of longer and longer necks.

 

It's the wrong idea, not the wrong term. Mutations have nothing to do with the environment. They are part of the genes and the combination of them. The environment just selects for certain mutations.

If as you say - The environment just selects for certain mutations – then it stands to reason that the environment is the initiating cause. Sorry I can’t see mutations occurring without initiating environmental pressure.

 

Sounds a lot like intelligent design if you ask me. You make so many unsupported assumptions, and that is what is causing your confusion.

Wow! Where did you get that? Cause and effect are divine are they? Physical and chemical causes are divine, are they? Strike a light!

 

To be clear, they are all selective. There is no need for distinction.

 

Well, that’s not what Darwin seemed to infer. I was attempting to clarify. So, you think random and selective are both selective, Darwin thinks random is separate from selective, when it comes to causes of advantageous gene loss?

 

It's not, though. The way the genes are passed and combined is the trigger for the mutation. The environment is simply the context in which those mutations are selected for or against.

 

I take your point, but I'm not convinced. The environment is more than just context. The environment is root cause for the process of genes being passed and combined in order to trigger mutation. If there isn't an environmental cause the passing, combining wouldn't take place for the mutation to occur.

[iNow]

Despite my points, you're still arguing from exactly the same place you were before.

 

Ok, point taken. A population needs to be of a ‘functional’ size for it's environment. But, small populations are still at a greater disadvantage, particularly if something as simple as a chance rock fall causes them catastrophe.

Here, you concede you were mistaken, then immediately reassert the very same point. I'm not going to argue with you.

 

 

 

 

Wow! Where did you get that? Cause and effect are divine are they? Physical and chemical causes are divine, are they? Strike a light!

 

It was in response to your statement:

 

"Chance has a cause."

[dichotomy]

Here, you concede you were mistaken, then immediately reassert the very same point. I'm not going to argue with you.

 

No, I simply state that as a rule large population are best. As a rule, populations that are so small as to be devastated by a chance event are not. What I concede is that there are exceptions.

 

 

It was in response to your statement:

 

"Chance has a cause."

 

And a rather assuming and over the top respose it was too.

To clarify - Rock falls, as such, are not chance. But, the timing of being there, at that time, is chance. And no, there is no evidence of divine intervention involved in this process.

 

 

This is all besides the point really, what I was originally arguing is that advantageous alleles are obviously lost due to physical environmental cause, or a process that is triggered by physical environmental cause. All examples thus far have IMO an original environmental cause.

 

Originally Posted by dichotomy

I’d think a successful species, initially, need a challenging, unpredictable environment to trigger the development of advantageous genes.

 

What is the basis of this assumption?

 

 

"Evolution takes place under changing environmental conditions, forcing organisms to continually readapt. Intuitively, this would slow things down even further, as successive generations must switch tack again and again in the struggle to survive. But when Kashtan, Noor and Alon created a simulation in which the goals changed repeatedly, they found that its evolution actually speeded up. They even found that the more complex the goal -- i.e., the more generations needed reach it under fixed conditions -- the faster evolution accelerated in response to changes in that goal. "

 

http://www.sciencedaily.com/releases/2007/08/070828084425.htm

[CDarwin]

Dichotomy, I think you've just misunderstood Paralith. As far as I can tell, she (I think that's a she) was talking about genetic drift which is the 'random' (i.e. non-selective) process whereby alleles are removed from a population.

 

The environment does not cause mutations (except in rare cases of exposure to mutagens), it only selects for them, and if an allele is rare enough, either because it is newly arisen or currently neutral or disadvantageous, then it can be wiped out by a single 'random' event. What you have to understand is that "advantageous" is not an absolute concept. What is neutral or disadvantageous today may be a god-send two generations down the line when the environment changes. That's a simplistic explanation but those concepts seem to be at the heart of your misunderstanding.

 

Your link is interesting, but it doesn't change these basic facts.

[vampares]

Many species have a dominance/territorial means of self selection. Those who are health occupy a "territory" in which the individual, mate(s) and their offsping may live. This should create gradients of gene pools and even niches for each.

 

Along the lines of loss of "advantageous" genes, diabetes is an example, perhaps similar to Vitamin C. Of course diabetics would have died prior to Humalin. But scurvy was not uncommon just a century ago.

 

This mode of "loss" is by genetic disease -- even if simply by definition.

 

People who are genetically or otherwise physiologically impaired are sometimes referred to as "parasites". Not exactly politically correct. Still, intercities are strife with mentally ill, physically disabled, etc. A good example is war veterans. Throughout history it is recorded that sick people congregate near hubs of commerce (even making their way upstream if need be). It was more of a "problem" a few years ago. Interestingly these "herds" have a quivering anxiety to them. There is no "peace". The same thing occurs with animals who are genetically or physically compromised.

 

Matthew 18:20

For where two or three are gathered together in my name, there am I in the midst of them.

 

What is neutral or disadvantageous today may be a god-send two generations down the line when the environment changes.

 

Prior genetic pressure, ie black in Africa may have a mutation in melanin that makes him "blacker". This mutation is only going to be noticed in the depths of the Sahara. In a European it would make him or her look unwell. As would albinism in Africa. Neither of these things are going to rock anyones world as we can see by the proliferation of whites, blacks and mulatto's -- the two most genetically distinct populations (there is a chart, if I can find it).

 

This pressure sensitive selection is key. It all depends on the pressure. Many genetic diseases that are found in humans mock the traits healthy individuals. Each disease has a corresponding trait. This may allow for pseudo-selection, or it may mask the underlying condition. "Asian" eyes, nordic dolichocephally, youth types (either retarded or psuedo-puerile), etc., even stupidity or passive disposition can be an advantage. This the "genetic drift" that is anchored down. It is a loss of good genetic material. The advantage is not really there but the "evolution" is, at any rate.

[iNow]

Along the lines of loss of "advantageous" genes, diabetes is an example, perhaps similar to Vitamin C. Of course diabetics would have died prior to Humalin.

 

Uhhmmm.... I'm guessing you mean the broader concept of injectable insulin? Humulin, itself just a specific brand made by Eli Lilly, is a relatively recent addition to diabetes treatment.

[vampares]

Uhhmmm.... I'm guessing you mean the broader concept of injectable insulin? Humulin, itself just a specific brand made by Eli Lilly, is a relatively recent addition to diabetes treatment.

 

OK, yeah. This is recombinant instead of from animal sources? But yeah this is the idea I was getting at.

 

It is almost deflating to even suggest that diabetes is a necessary evil; that evolution is inevitable. I can't strap diabetes to corprate behavior, and simply wash my hands of it. On economic terms, indenturing people even by dependence "creates jobs", as the cynics mantra goes.

[dichotomy]

Dichotomy, I think you've just misunderstood Paralith. As far as I can tell, she (I think that's a she) was talking about genetic drift which is the 'random' (i.e. non-selective) process whereby alleles are removed from a population.

 

I think I just misunderstood Paralith regarding what was so random about a rockfall. Of course now, I think she meant the timing of the event with the timing of the groups movement was what is random. So, timing is the random cause that wiped out advantageous alleles.

 

The environment does not cause mutations (except in rare cases of exposure to mutagens), it only selects for them, and if an allele is rare enough, either because it is newly arisen or currently neutral or disadvantageous, then it can be wiped out by a single 'random' event.

 

Ok, is ‘the environment selects for mutation’, the same as saying, ‘the environment causes the random mutation selection to occur’? Again, I am back at the logic of the environment being the initial cause/trigger, and the ‘random’ (biological definition) mutation being the eventual outcome? And, for the paranoids, I'm not saying that the environment is GOD. The environment just IS.

 

What you have to understand is that "advantageous" is not an absolute concept. What is neutral or disadvantageous today may be a god-send two generations down the line when the environment changes.

 

I understand and agree with all of this.

 

Your link is interesting, but it doesn't change these basic facts.

 

Well, what it suggests is that more external changing pressures cause more rapid adaptation. Again, to a non-scientist like me, it seems to tell me that environmental pressures are the keys which trigger the advantageous mutations. There is no true, magical randomness here, there are enviro causes. What there is, are mutations that are either successful or unsuccessful for their space in time. And without successful adaptations, there is no life.

[CDarwin]

Ok, is ‘the environment selects for mutation’, the same as saying, ‘the environment causes the random mutation selection to occur’? Again, I am back at the logic of the environment being the initial cause/trigger, and the ‘random’ (biological definition) mutation being the eventual outcome? [/Quote]

 

No. Mutations occur because of errors in the DNA replication process. That has nothing to do with the environment. Selection results in the fact that some mutations will end up more prevalent than others. (Again, that's simplistic, but it's the gist of the relationship between mutation, selection, and environment).

 

Well, what it suggests is that more external changing pressures cause more rapid adaptation.

 

That's right, but it isn't the environment causing 'advantageous' mutations. The mutations just happen. Some individuals with some of the mutations do better than others without them in the environment into which they are born.

 

The rapidly changing environment means that there are few generations of evolutionary stasis because optimality is so hard to come by and what is 'advantageous' is constantly changing. That means selection is acting more vigorously than usual.

 

The environment is affecting selection, not mutation.

[dichotomy]

No. Mutations occur because of errors in the DNA replication process. That has nothing to do with the environment. Selection results in the fact that some mutations will end up more prevalent than others. (Again, that's simplistic, but it's the gist of the relationship between mutation, selection, and environment).

 

 

 

That's right, but it isn't the environment causing 'advantageous' mutations. The mutations just happen. Some individuals with some of the mutations do better than others without them in the environment into which they are born.

 

The rapidly changing environment means that there are few generations of evolutionary stasis because optimality is so hard to come by and what is 'advantageous' is constantly changing. That means selection is acting more vigorously than usual.

 

The environment is affecting selection, not mutation.

 

Thanks for the clarification here.

 

I'm not 100% convinced that DNA 'errors' are errors, although I accept that scientists have a much higher probability of being correct here than I of course.

 

 

Regarding the Vit C production genes going missing. Is there absolutely no humans that have this ability?

[iNow]

I'm not 100% convinced that DNA 'errors' are errors

They're not errors. They're mutations. Error is a subjective label applied to the mutation by a human mind.

[vampares]

SNP are single nucleotide mutations. Spliced DNA and broken chromosomes are mutations. Triplet repeats are mutations.

 

Mutation are Errors. It is not something that is judged and scored like a grade, calculated, or something that can be erased and simply corrected (after it is said and done). It is something that an organism has to live with. Perhaps this is a good thing but organisms will not share this mutation unless it is passed on to offspring. And it is still unique. It is a divergence.

 

But it is the nature of the mechanism by which these things occur is widely regarded as anomalous. There are no theories for controlled mutation or adaptation.

 

What is more the "trinucleotide repeat expansion" is termed a "missense" mutation. That is it contains nothing that can be used as genetic information. Unlike "nonsense" or randomness, triplet repeats contain what is in effect a tautology.

 

The ^@^@^@^@^@^@^@^@^@^@^@^@ writeback to files that are in volatile memory but are filesystem linked which occurs when the linux kernel crashes is a good analogy. Messing up you harddrive. The information that is written back is not random (monkey on a typewriter)

011010011101111010101011101110001,

it is only

0000000000000000000000000000000. 011010011101111010101011101110001 might actually mean something, probably doesn't but it could.

 

Try doing that to your harddrive. Just switch a bit somewhere -- anywhere.

• You might have switched the bit in an empty spot on you disk. No harm done. The computer will never know.
  
• You might have switched the bit in a JPG photo. The photo may not be readable any longer or it may look different or it may not change at all.
  
• You might have switched the bit in part of the MS Word software. Part or all of MS Word may crash. It may act differently or it may not change at all.
  
• You might have switched the bit in part of the File System. You may not be able to access certain files, file attributes may have been altered, you may not be able to access any part of the filesystem at all.
  
• You may have altered a Microsoft Windows file. Nowadays Windows checks everytime uses a file and freaks if it isn't the same. Otherwise you may not be able to start your computer or you may have limited access to certain functionality.

 

I don't like analogies because they never fit quite right.

 

Triplet repeats add DNA in some cases. It inserts the triplets. This breaks stuff. It is not a function of normal DNA, it is a result of defective DNA maintenance. The same function in normal cells with normal DNA does something else and it is not this.

 

Cells will even try to make the proteins in some instances -- with the repeated aminoacid. That is something that destroys the cells function. Disease is probably a better word.

[vampares]

SNP are single nucleotide mutations. Spliced DNA and broken chromosomes are mutations. Triplet repeats are mutations.

 

Mutation are Errors. It is not something that is judged and scored like a grade, calculated, or something that can be erased and simply corrected (after it is said and done). It is something that an organism has to live with. Perhaps this is a good thing but organisms will not share this mutation unless it is passed on to offspring. And it is still unique. It is a divergence.

 

But it is the nature of the mechanism by which these things occur is widely regarded as anomalous. There are no theories for controlled mutation or adaptation.

 

What is more the "trinucleotide repeat expansion" is termed a "missense" mutation. That is it contains nothing that can be used as genetic information. Unlike "nonsense" or randomness, triplet repeats contain what is in effect a tautology.

 

The ^@^@^@^@^@^@^@^@^@^@^@^@ writeback to files that are in volatile memory but are filesystem linked which occurs when the linux kernel crashes is a good analogy. Messing up you harddrive. The information that is written back is not random (monkey on a typewriter)

011010011101111010101011101110001,

it is only

0000000000000000000000000000000. 011010011101111010101011101110001 might actually mean something, probably doesn't but it could.

 

Try doing that to your harddrive. Just switch a bit somewhere -- anywhere.

• You might have switched the bit in an empty spot on you disk. No harm done. The computer will never know.
  
• You might have switched the bit in a JPG photo. The photo may not be readable any longer or it may look different or it may not change at all.
  
• You might have switched the bit in part of the MS Word software. Part or all of MS Word may crash. It may act differently or it may not change at all.
  
• You might have switched the bit in part of the File System. You may not be able to access certain files, file attributes may have been altered, you may not be able to access any part of the filesystem at all.
  
• You may have altered a Microsoft Windows file. Nowadays Windows checks everytime uses a file and freaks if it isn't the same. Otherwise you may not be able to start your computer or you may have limited access to certain functionality.

 

I don't like analogies because they never fit quite right.

 

Triplet repeats add DNA in some cases. It inserts the triplets. This breaks stuff. It is not a function of normal DNA, it is a result of defective DNA maintenance. The same function in normal cells with normal DNA does something else and it is not this.

 

Cells will even try to make the proteins in some instances -- with the repeated aminoacid. That is something that destroys the cells function. Disease is probably a better word.

[CDarwin]

They're not errors. They're mutations. Error is a subjective label applied to the mutation by a human mind.

 

I think its fair to call it an "error." If DNA replication was 100% infallible then you would never have any mutations. Mutations occur because replication is imperfect; there are "errors."