Mutations and Evolution (formerly called Evolution)

[Bio freck]

How mutation helps in evolution?

[Moontanman]

How mutation helps in evolution?

 

 

Mutations, among other things, produces variation in organisms, these variations when filtered by natural selection, sexual selection, and allele frequency produce organisms better suited for the environment and allows them to survive to pass their DNA to their offspring.

[Phi for All]

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Moderator Note

Since you have a very specific question about evolution, I'm going to change the name of this thread to help get you specific answers. Please think about this on any future threads you start.

[Bio freck]

Mutations, among other things, produces variation in organisms, these variations when filtered by natural selection, sexual selection, and allele frequency produce organisms better suited for the environment and allows them to survive to pass their DNA to their offspring.

 

Would sickle cell anemia be its example?

[CharonY]

Technically the whole gene pool is the result of mutations. Every single of our genes, regardless whether they lead to diseases or not.

[Bio freck]

Technically the whole gene pool is the result of mutations. Every single of our genes, regardless whether they lead to diseases or not.

 

Gene pool!Mutation is a sudden and spontaneous change responsible for changing a gene (defective or beneficial),How would it affect a gene pool?

[CharonY]

Mutations are sudden in nature (either tthey are there or not). However, usually it is not very useful to look at at the rise of a single allele in a single individual. Instead you want to look at the frequencies in a given population. So basically how often does this mutation occur per generation and how it affects fitness. Also the population size is important. If the frequency of the mutation is low, it is only likely to persist if it carries a high increase of fitness (e.g. it is selected for) and vice versa.

[Halucigenia]

How mutation helps in evolution?

To put it simply (hopefully); evolution is the change of allele frequencies within populations of organisms over time. Alleles are different versions of genes. Different versions of genes arise via mutation. Different versions of genes provide variation within populations of organisms. Therefore, mutation "drives" evolution by being the source of variation from which natural selection and genetic drift can change the frequency of different alleles within populations of organisms over time thus giving rise to the genetic diversity that we see throughout the living world. Once different populations of organisms become sufficiently different as not to breed with each other speciation can occur and the resulting populations of organisms can continue to diverge genetically since their genes no longer mix in a single gene pool. This is all due to those mutations occurring in the fist place to provide the variation to enable evolution to proceed.

Thus mutation is not just a help, it is essential for evolution.

 

Would sickle cell anemia be its example?

Sickle cell anaemia is a very good example of a mutation, one that even though it is potentially harmful, is retained in the population because it is also beneficial given the right environment i.e. that of the presence of malarial infection. This illustrates well the fact that mutations can only be said to be beneficial or detrimental with respect to fitness, that is the fitness of the organism to it's environment, as given one environment – one without a high incidence of malarial infection the mutations potential detrimental effect of sickle cell anaemia would be perceived to be detrimental. While in an environment with a prevalence of malarial infection it is positively beneficial for individuals to have the mutation in at least one of their alleles (heterozygotes).

Sickle cell anaemia is also illustrative of the effect of overdominance of genes that have different alleles affecting homozygous and heterozygous individuals differently homozygotes having either no protection from malaria (ones with both alleles not having the mutation) or a dramatic propensity to sickle cell anemia (ones with both alleles having the mutation, and heterozygotes (ones having both a mutated allele and a non mutated allele) having a partial resistance to both. This is very instructive in an understanding of how evolution operates due to changes in alleles frequencies.

 

Gene pool!Mutation is a sudden and spontaneous change responsible for changing a gene (defective or beneficial),How would it affect a gene pool?

See above. While mutation is “a sudden and spontaneous change responsible for changing a gene” it has potential to change the frequency of alleles in a population of organisms over time as it can be passed on to subsequent generations and may, if beneficial or neutral and “lucky” (see genetic drift) increase in frequency in the gene pool over the generations.

As CharonY says, it is useful to look at evolution as an effect on a population's gene pool over time rather than to concentrate on an individual with a mutation.

[jimmydasaint]

What about Huntington's Disease, Motor Neuron Disease, Alzheimer's Disease and Polydactyly?

[Halucigenia]

What about Huntington's Disease, Motor Neuron Disease, Alzheimer's Disease and Polydactyly?

What about them?

Are you trying to ask me something?

[jimmydasaint]

You gave an excellent answer to the previous few posts. However, IMO, many mutations are either neutral or downright deleterious. I believe there should be caution and some balance when human mutations are mentioned Halucigenia.

[Moontanman]

Would sickle cell anemia be its example?

 

 

Yes sickle cell anemia would be an example of a mutation that has spread through certain populations. it confers both an advantage and a disadvantage to individuals with this mutation. Each human zygote starts out with about 130 mutations.

 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1288368/

 

Most mutations are neutral and have no effect on the organism.

[Halucigenia]

You gave an excellent answer to the previous few posts.

Thank you.

However, IMO, many mutations are either neutral or downright deleterious. I believe there should be caution and some balance when human mutations are mentioned Halucigenia.

I'm still not sure if I am understanding you there.

I agree that "many mutations are either neutral or downright deleterious" but I still maintain that in respect to evolutionary theory it is a fact "that mutations can only be said to be beneficial or detrimental with respect to fitness".

Of the illnesses that you mention this is still the case for the ones that are known to be caused by mutations. I does not matter to evolutionary theory that for example Huntington's Disease is a pernicious and downright horrific disease for someone to suffer and of course we all should sympathise with anyone that it affects.

 

In evolutionary theory the fitness of the organism to it's environment simply takes into account how likely it is to survive long enough to reproduce successfully and whether its offspring can themselves survive and and are fit enough compete with others long enough to reproduce.

 

The fact that any mutation that in the majority of cases does not cause dramatic disability to those it affects until after reproductive age means that it is not particularly deleterious as far as evolution is concerned, as individuals with this kind of mutation throughout human evolutionary history could have passed it on fairly transparently to any selection pressures.

I don't mean to sound harsh but those are the facts and no amount of “caution or balance” changes those facts.

On a science forum such as this I would expect that we can be candid enough to explain the facts as they appear without being so over-cautious that the explanations might cause offence so as to obfuscate a good explanation by declaring any particular mutation deleterious when, in the proper scientific meaning of the word in this context, it is not.

[questionposter]

Thank you.

 

I'm still not sure if I am understanding you there.

I agree that "many mutations are either neutral or downright deleterious" but I still maintain that in respect to evolutionary theory it is a fact "that mutations can only be said to be beneficial or detrimental with respect to fitness".

Of the illnesses that you mention this is still the case for the ones that are known to be caused by mutations. I does not matter to evolutionary theory that for example Huntington's Disease is a pernicious and downright horrific disease for someone to suffer and of course we all should sympathise with anyone that it affects.

 

In evolutionary theory the fitness of the organism to it's environment simply takes into account how likely it is to survive long enough to reproduce successfully and whether its offspring can themselves survive and and are fit enough compete with others long enough to reproduce.

 

The fact that any mutation that in the majority of cases does not cause dramatic disability to those it affects until after reproductive age means that it is not particularly deleterious as far as evolution is concerned, as individuals with this kind of mutation throughout human evolutionary history could have passed it on fairly transparently to any selection pressures.

I don't mean to sound harsh but those are the facts and no amount of "caution or balance" changes those facts.

On a science forum such as this I would expect that we can be candid enough to explain the facts as they appear without being so over-cautious that the explanations might cause offence so as to obfuscate a good explanation by declaring any particular mutation deleterious when, in the proper scientific meaning of the word in this context, it is not.

 

So, if a mutation is your that skin color is #ffcf91 as opposed to the normal #f4c282, your more or less likely to survive? How does hair color effect your fitness? Not every mutation is particularly useful or not useful for something.

Edited April 1, 2012 by questionposter

[Halucigenia]

So, if a mutation is your that skin color is #ffcf91 as opposed to the normal #f4c282, your more or less likely to survive? How does hair color effect your fitness? Not every mutation is particularly useful or not useful for something.

Ah, I think that I see the misunderstanding, thanks questionposter, I wonder if jimmydasaint has the same misunderstanding.

 

Do you think that I meant that mutations are only ever either beneficial or detrimental according to evolution, and never neutral?

 

What I meant was that to be able to tell if a mutation is beneficial or detrimental with respect to evolution you have to understand the environmental pressures that the population of organisms in question is under. As I explained in the sickle cell anaemia example it can be either depending if malarial infection is prevalent in the population. I thought it should be obvious that they can also be neutral as I alluded to above with respect to mutations that are only cause debilitating effects after reproductive age.

 

Of course slight variations in skin and hair colour can be determined to be beneficial or detrimental evolutionarily wise. For example all it takes is for the majority of sexual partners to have a penchant for a slightly different hair, skin, or feather (think peacocks and birds of paradise) colour for the frequency of the alleles for that particular mutation to increase in the population over the generations via sexual selection. That, in a nutshell is how evolution via sexual selection works. Also with other types of selection all it can take is a very slight phenotypic difference to effect an evolutionary change.

 

Anyway I think that the keyword in the above few posts is “deleterious” as it has a very specific evolutionary meaning. It does not just mean that the mutation has a harmful effect on an individual organism but it means that this harmful effect affects the fitness of that organism where fitness in evolutionary theory, as I have explained above, also has a specific meaning.

“In evolutionary theory the fitness of the organism to it's environment simply takes into account how likely it is to survive long enough to reproduce successfully and whether its offspring can themselves survive and and are fit enough compete with others long enough to reproduce.”

 

Furthermore, it can only take very slight phenotypic or behavioural changes to affect that fitness enough for mutated alleles to increase in frequency in a population over the generations. This depends on the environment in which those mutated genes find themselves in. Therefore, whether a mutation is determined to be neutral, beneficial, detrimental or deleterious depends on the above factors. Determining this is not as clear cut as some people may claim.

 

I think that we are getting sidetracked here but I hope that I have made my explanation clearer now than previously.

[CharonY]

Very good answer(s). Edit: I wanted to vote the post up, but being tired I clicked the wrong button. Sorry about that.

Edited April 2, 2012 by CharonY

[jimmydasaint]

Ah, I think that I see the misunderstanding, thanks questionposter, I wonder if jimmydasaint has the same misunderstanding.

 

Do you think that I meant that mutations are only ever either beneficial or detrimental according to evolution, and never neutral?

 

Again, another excellent answer. I would consider that most mutations are neutral. However, I did not read the last paragraph of one of your responses and just wanted to point out that there is a large number of human mutations that do affect fitness and decrease the opportunity for successful reproduction, in the current environment.

 

For example, there are a number mentioned in wiki:

 

Wiki List of Genetic Disorders

 

That is all I meant by 'balance'. Of course you have to be candid about the contribution that those affected could make to the gene pool and define evolutionary fitness.

 

 

Of course slight variations in skin and hair colour can be determined to be beneficial or detrimental evolutionarily wise. For example all it takes is for the majority of sexual partners to have a penchant for a slightly different hair, skin, or feather (think peacocks and birds of paradise) colour for the frequency of the alleles for that particular mutation to increase in the population over the generations via sexual selection. That, in a nutshell is how evolution via sexual selection works. Also with other types of selection all it can take is a very slight phenotypic difference to effect an evolutionary change.

 

I don't know how relevant this article is, but it suggests that the skin colour of the Europeans may have evolved to increase the 'fitness' to make vitamin D in light-deprived areas.

 

 

According to a team of researchers from Copenhagen University, a single mutation which arose as recently as 6-10,000 years ago was responsible for all the blue-eyed people alive on Earth today.

 

The team, whose research is published in the journal Human Genetics, identified a single mutation in a gene called OCA2, which arose by chance somewhere around the northwest coasts of the Black Sea in one single individual, about 8,000 years ago.

 

The gene does not "make" blue in the iris; rather, it turns off the mechanism which produces brown melanin pigment. "Originally, we all had brown eyes," says Dr Hans Eiberg, who led the team...

 

It is only in Europe that you will find large numbers of blondes and redheads, brunettes, pale skins and olive skins, blueeyed and green-eyed people living together in the same communities. Across the rest of the world people are almost uniformly darkhaired and dark-eyed.

Why this should be remains unknown, and in particular how such mutations can have arisen so quickly since Europe was colonised by Africans just a few tens of thousands of years ago.

 

One theory is that Europe's cold weather and dark skies played a part. Fair skin is better at making Vitamin D from the 8 per cent of the world's population have blue eyes weak sunlight found in northern latitudes.

 

Link

 

and Link to Paper

Edited April 2, 2012 by jimmydasaint

[Halucigenia]

Ah, after re-reading this thread I do see a potential for misunderstanding what I meant if this one statement is taken out of context;

 

“that mutations can only be said to be beneficial or detrimental with respect to fitness”.

 

If you read that with the wrong emphasis as I have tried to indicate above you could get the wrong interpretation.

 

What I meant by that was that;

 

mutations can be said to be beneficial or detrimental [or neutral] only with respect to fitness

 

I can see now how this might have been misinterpreted.

 

I hope that clears up any misunderstanding.

 

Again, another excellent answer.

Thank you again.

I would consider that most mutations are neutral.

Me too.

However, I did not read the last paragraph of one of your responses and just wanted to point out that there is a large number of human mutations that do affect fitness and decrease the opportunity for successful reproduction, in the current environment.

Yes, of course there are.

 

For example, there are a number mentioned in wiki:

 

Wiki List of Genetic Disorders

 

That is all I meant by 'balance'. Of course you have to be candid about the contribution that those affected could make to the gene pool and define evolutionary fitness.

I'm glad that you do appear to understand me.

 

I don't know how relevant this article is, but it suggests that the skin colour of the Europeans may have evolved to increase the 'fitness' to make vitamin D in light-deprived areas.

Link

 

and Link to Paper

Good point. It also may be that light coloured skin and other northern European traits are somehow linked and that if lighter skin gave evolutionary advantage by increasing vitamin D production then the other traits just hitched a ride so to speak.