How does natural selection determine which mutations remain and which do not?

[pshun2404]

Seriously! Seriously! This is one question I have never found a satisfactory explanation for. By natural selection? But how does the cell accomplish this? If not by natural selection then are they acquired? But they are inheritable???? We know DNA repair processes weed most of them out so are those that remain just a happy little accident?

What processes, mechanisms, enzymes, etc., are involved in their formation and in allowing those that stay?

This is not meant to be a number of questions but rather I am looking for an explanation of how they form initially and remain as opposed to others and whether it is just a random event?

 

[pshun2404]

I did get a response on another thread from one biologist who obviously misunderstanding said "The Cell doesn't choose what mutations remain selected, the cell is a product of selected mutations."

But I have seen a number of articles and videos describing inheritance of mutations that already exist, how some form in meiosis and mitosis, and some via environmental acquisition already. But how were these selected (cellularly speaking)? They certainly did not exist before the cell itself!

How did they come about and what processes, mechanisms, enzymes, etc., are involved in allowing those that stay? I guess I am looking for an explanation of how they formed initially and why they remain as opposed to others ( as a matter of biochemical function) or whether it is assumed to be just a random event...

Anyone have any thoughts?

 

[sfs]

I can't say that I really understand your question(s). Mutations are changes to DNA. They can occur while DNA is replicating, which means while a cell is being formed. Which ones occur, and make it past DNA polymerase proofreading, is basically random, although some changes are more likely to occur than others.

Mutations also happen while a cell is fully formed, as damage occurs to the DNA; this can occur in a variety of ways, through mutagenic chemicals, through ionizing radiation, through double-stranded breaks to the DNA that are not correctly repaired, through spontaneous chemical change. These too are basically random, but with some types of change more likely than others.

All of these changes can be passed to daughter cells, should the cell replicate. If the cell is in a multicellular organism, and is a germ-line cell, the changes can be passed to offspring.

None of these processes involve natural selection. Natural selection just means that changes that hurt the organism are less likely to be passed on from generation to generation, since they mean the organism is at a disadvantage and won't leave as many (or any) offspring.

 

[tas8831]

Anyone have any thoughts?

My initial thought is that you, with 30 years science reading and talking to scientists and doing lab work, should not be asking such questions.

 

[PsychoSarah]

Seriously! Seriously! This is one question I have never found a satisfactory explanation for. By natural selection? But how does the cell accomplish this? If not by natural selection then are they acquired? But they are inheritable???? We know DNA repair processes weed most of them out so are those that remain just a happy little accident?

What processes, mechanisms, enzymes, etc., are involved in their formation and in allowing those that stay?

This is not meant to be a number of questions but rather I am looking for an explanation of how they form initially and remain as opposed to others and whether it is just a random event?

-_- the mutations that benefit survival and reproduction persist, and those which are a severe detriment to those do not. It's just basic sense in a world in which organisms are all in competition with each other for resources. If I die before I can reproduce thanks to a mutation unique unto myself, that mutation will not persist. That's what natural selection is, no more, and no less. Detrimental mutations can persist, however, as long as they don't entirely prevent survival and reproduction, as is the case with many recessive diseases. Additionally, since traits can be detrimental or beneficial depending on what environment one lives in, populations in different environments will have selective pressures which favor different traits.

 

[tas8831]

I did get a response on another thread from one biologist who obviously misunderstanding said "The Cell doesn't choose what mutations remain selected, the cell is a product of selected mutations."

But I have seen a number of articles and videos describing inheritance of mutations that already exist, how some form in meiosis and mitosis, and some via environmental acquisition already. But how were these selected (cellularly speaking)? They certainly did not exist before the cell itself!

How did they come about and what processes, mechanisms, enzymes, etc., are involved in allowing those that stay? I guess I am looking for an explanation of how they formed initially and why they remain as opposed to others ( as a matter of biochemical function) or whether it is assumed to be just a random event...

Anyone have any thoughts?

I find this group of questions bizarre.

Mutations happen. There are numerous known and understood "sources" of mutation - the most common being replication error. A simple resource on this is here.

Mutations occur without regard to fitness. Essentially mutations can occur anywhere in the genome (with some caveats relating primarily to things like overall local sequence).
That is, mutations happen and there is no evidence that where they occur is chosen to influence cellular activity for good or bad or neutral (why would a cell choose a bad mutation if it is conscious?).

If a mutation occurs in a sperm or egg (germline), it is potentially heritable. If it happens in a skin cell (somatic), it is not.

After DNA has been replicated, the DNA is 'checked' by enzymes for fidelity - but understand that these enzymes do not know what the 'correct' sequence should be, they respond to physical aberrations in the structure of the DNA (since mismatched nucleotides, in essence, produce a bump).

Again - why do you not know this with 30 years of science reading and biology/biochem lab experience? This is freshman level stuff.

In fact, now that I see i spent 5 minutes typing, it is easier just to refer you to this site which probably has most of the answers to your 'questions' -


Understanding Evolution

 

[pshun2404]

I can't say that I really understand your question(s). Mutations are changes to DNA. They can occur while DNA is replicating, which means while a cell is being formed. Which ones occur, and make it past DNA polymerase proofreading, is basically random, although some changes are more likely to occur than others.

Mutations also happen while a cell is fully formed, as damage occurs to the DNA; this can occur in a variety of ways, through mutagenic chemicals, through ionizing radiation, through double-stranded breaks to the DNA that are not correctly repaired, through spontaneous chemical change. These too are basically random, but with some types of change more likely than others.

All of these changes can be passed to daughter cells, should the cell replicate. If the cell is in a multicellular organism, and is a germ-line cell, the changes can be passed to offspring.

None of these processes involve natural selection. Natural selection just means that changes that hurt the organism are less likely to be passed on from generation to generation, since they mean the organism is at a disadvantage and won't leave as many (or any) offspring.

Thanks SFS for a real quality answer that yes apparently did not understand the question. So your answer is actually "Which ones occur, and make it past DNA polymerase proofreading, is basically random, although some changes are more likely to occur than others."

So basically, in your opinion (which I respect) occurrence is random and the "more likely" is a matter of probability, and you cannot really describe any enzymes or systematic functions that perform this process. Thanks.

 

[pshun2404]

I find this group of questions bizarre.

Mutations happen. There are numerous known and understood "sources" of mutation - the most common being replication error. A simple resource on this is here.

Mutations occur without regard to fitness. Essentially mutations can occur anywhere in the genome (with some caveats relating primarily to things like overall local sequence).
That is, mutations happen and there is no evidence that where they occur is chosen to influence cellular activity for good or bad or neutral (why would a cell choose a bad mutation if it is conscious?).

If a mutation occurs in a sperm or egg (germline), it is potentially heritable. If it happens in a skin cell (somatic), it is not.

After DNA has been replicated, the DNA is 'checked' by enzymes for fidelity - but understand that these enzymes do not know what the 'correct' sequence should be, they respond to physical aberrations in the structure of the DNA (since mismatched nucleotides, in essence, produce a bump).

Again - why do you not know this with 30 years of science reading and biology/biochem lab experience? This is freshman level stuff.

In fact, now that I see i spent 5 minutes typing, it is easier just to refer you to this site which probably has most of the answers to your 'questions' -


Understanding Evolution

Already read that and many more multiple times, but thanks for your perspective I appreciate the explanation. So you also are of the "happens randomly"crowd, and as far as which one's remain is pretty much hit or miss, thus "natural selection" does NOT cause or determine which ones remain and which ones do not! Cool!

 

[tas8831]

Already read that and many more multiple times, but thanks for your perspective I appreciate the explanation. So you also are of the "happens randomly"crowd, and as far as which one's remain is pretty much hit or miss.

They happen randomly with regard to fitness.

It is not hit to miss as to which remain, it is largely dependent on whether or not they affect fitness. Neutral mutations accumulate at higher rates over time than detrimental ones since they do not affect fitness and are thus under no selective pressure.

Given your history, I suspect that at some point you are going to spring upon us some fringe 'reputable scientist' who claims otherwise and side with him or her regardless of their actual evidence.

 

[pshun2404]

They happen randomly with regard to fitness.

It is not hit to miss as to which remain, it is largely dependent on whether or not they affect fitness. Neutral mutations accumulate at higher rates over time than detrimental ones since they do not affect fitness and are thus under no selective pressure.

Given your history, I suspect that at some point you are going to spring upon us some fringe 'reputable scientist' who claims otherwise and side with him or her regardless of their actual evidence.

If no natural selection is involved, please define "selective pressure"? Is there a difference in your thinking?

 

[jacks]

To the OP
What an interesting question. To be honest at this point I think the answer is an unsatisfying "we don't know". However, given the promiscuity of some enzymes perhaps they may evolve in beneficial ways, though even in evolutionary terms that probability would be extremely low. THIS paper suggests there may be secondary alternative reactions that would allow a selective advantage. I think you may find the whole paper interesting especially her conclusions.

 

[jax5434]

Seriously! Seriously! This is one question I have never found a satisfactory explanation for. By natural selection? But how does the cell accomplish this? If not by natural selection then are they acquired? But they are inheritable???? We know DNA repair processes weed most of them out so are those that remain just a happy little accident?

What processes, mechanisms, enzymes, etc., are involved in their formation and in allowing those that stay?

This is not meant to be a number of questions but rather I am looking for an explanation of how they form initially and remain as opposed to others and whether it is just a random event?

Evolution is not teleological. It determines nothing, it preserves nothing it has no end game in mind.
God Bless
Jax

 

[gaara4158]

Which mutations occur is random. Whether that mutation is passed on to subsequent generations is determined by that mutation’s effect on the organism’s ability to reproduce. If the mutation is helpful, it is passed on to subsequent generations and “remains” as a part of the population’s gene pool. If it is detrimental, then it usually ends with that organism as it fails to pass on its genes. This process is called natural selection, so I don’t know why you’re insisting that the answer to your question can’t be natural selection.

 

[pshun2404]

To the OP
What an interesting question. To be honest at this point I think the answer is an unsatisfying "we don't know". However, given the promiscuity of some enzymes perhaps they may evolve in beneficial ways, though even in evolutionary terms that probability would be extremely low. THIS paper suggests there may be secondary alternative reactions that would allow a selective advantage. I think you may find the whole paper interesting especially her conclusions.

Sorry no paper there...

 

[Halbhh]

Seriously! Seriously! This is one question I have never found a satisfactory explanation for. By natural selection? But how does the cell accomplish this? If not by natural selection then are they acquired? But they are inheritable???? We know DNA repair processes weed most of them out so are those that remain just a happy little accident?

What processes, mechanisms, enzymes, etc., are involved in their formation and in allowing those that stay?

This is not meant to be a number of questions but rather I am looking for an explanation of how they form initially and remain as opposed to others and whether it is just a random event?

"How can you believe since you accept glory from one another but do not seek the glory that comes from the only God?"
(This got copied in from another post, but...perhaps we should leave it in here)

Only a small portion of mutations would make it into a lived birthed new offspring. And those only sometimes a 'happy accident'. Many are not. To use a simple summary:

0) many mutations simply kill, but not all

1) bad mutations (for a specific environment) = poor thriving and/or death or reduced reproduction

2) neutral (to the current environment) mutations = no significant effect in the current environment on survival or reproduction, but sometimes can be good or bad for future offspring later in an altered environment

3) good mutations (for the current environment) = advantageous for survival and enhanced reproduction (more surviving offspring over time)

Notice a powerful effect from the random neutral mutations that will happen and accumulate over long periods of time in a species -- they cause the species to have a lot of available variety of traits that could help in new environments later in time! That's key to 'evolution'.

Eventually the environment changes, or the species is able to expand it's domain into new areas, due to this accumulation of new traits.

Notice that evolution is fully compatible with Genesis chapter 1!

There are many scenarios one can hypothesize that fit Genesis chapter 1 perfectly and have evolution also.

 

[yeshuaslavejeff]

This is not meant to be a number of questions but rather I am looking for an explanation of how they form initially and remain as opposed to others and whether it is just a random event?

God created them the way they are.

We will probably never know how or what natural selection would do, since we cannot observe it anywhere.

If someone makes up a myth of how it 'would' work, by man's definition , then that's how it 'would' work, by man's definition.....

 

[pshun2404]

Which mutations occur is random. Whether that mutation is passed on to subsequent generations is determined by that mutation’s effect on the organism’s ability to reproduce. If the mutation is helpful, it is passed on to subsequent generations and “remains” as a part of the population’s gene pool. If it is detrimental, then it usually ends with that organism as it fails to pass on its genes. This process is called natural selection, so I don’t know why you’re insisting that the answer to your question can’t be natural selection.

I'm not insisting on anything. So you are saying that if whether a "mutation is passed on to subsequent generations is determined by that mutation’s effect on the organism’s ability to reproduce."

So if it is helpful (in this way) it is passed on? And if it is not "it usually ends with that organism as it fails to pass on its genes." Right?

 

[Armoured]

Seriously! Seriously! This is one question I have never found a satisfactory explanation for. By natural selection? But how does the cell accomplish this? If not by natural selection then are they acquired? But they are inheritable???? We know DNA repair processes weed most of them out so are those that remain just a happy little accident?

What processes, mechanisms, enzymes, etc., are involved in their formation and in allowing those that stay?

This is not meant to be a number of questions but rather I am looking for an explanation of how they form initially and remain as opposed to others and whether it is just a random event?

It's pretty simple, beneficial mutations survive longer, non-beneficial mutations die earlier.

 

[sfs]

Thanks SFS for a real quality answer that yes apparently did not understand the question. So your answer is actually "Which ones occur, and make it past DNA polymerase proofreading, is basically random, although some changes are more likely to occur than others."

Since I didn't understand the question, I can't tell whether that's my answer or not. It's the answer to some question -- one that you seemed to be asking -- but whether it's the answer to the question you intended is hard to say.

So basically, in your opinion (which I respect) occurrence is random and the "more likely" is a matter of probability, and you cannot really describe any enzymes or systematic functions that perform this process. Thanks.

Which process? As I wrote, many different mutational processes are at work, which involve a variety of different enzymes, external agents and random factors.

 

[joshua 1 9]

What processes, mechanisms,

Do you want to know how the cell is regulated or do you want to know what regulates the DNA to turn it on and off? Or do you want to know how cells communicate with each other?

Each cell expresses, or turns on, only a fraction of its genes. The rest of the genes are repressed, or turned off. The process of turning genes on and off is known as gene regulation. Gene regulation is an important part of normal development. Genes are turned on and off in different patterns during development to make a brain cell look and act different from a liver cell or a muscle cell, for example. Gene regulation also allows cells to react quickly to changes in their environments. Although we know that the regulation of genes is critical for life, this complex process is not yet fully understood.