Are genetic mutations truly random or influenced by environment?

fret_wimp2

Are Genetic mutations truly random, or is there any influence?

as a (probably flawed example) which scenario is more correct:

1. Through random mutations, one member of a species develops more muscle mass. this trait is advantagous and so this member sires more offspring, leading eventually to the species evolving to have more muscle mass

2. Through performing intensive physical exertion, which can influence gene expression, members of a species become stronger and have more muscle mass. As these members breed, the genes which were off but expressed due to environmental factors become on by default causing the species to evolve to have more muscle mass.



Perhaps theres a better example scenario, but this is the best i could think of right now.

Capt'n Midnight

fret_wimp2 wrote: »

2. Through performing intensive physical exertion, which can influence gene expression, members of a species become stronger and have more muscle mass. As these members breed, the genes which were off but expressed due to environmental factors become on by default causing the species to evolve to have more muscle mass.

How does intensive physical exertion influence gene expression ?

Lamarckism was debunked yonks ago.



The nearest thing seen was perhaps in bacteria where the mutation rate went up during periods of starvation, but that was because starvation meant the normal gene repair mechanisms couldn't function.


Yes starvation of pregnant Dutch women at the end of world war II did result in smaller babies but that AFAIK didn't have any genetic component. Yes the children of the daughters were smaller but that was likely to be simply because their ovaries were formed during a term of malnutrition.

fret_wimp2

My example may well be quite flawed for sure.
I wasn't thinking of Lamarckism, more along the line of Epigenetics.

Capt'n Midnight

fret_wimp2 wrote: »

I wasn't thinking of Lamarckism, more along the line of Epigenetics.

It's more like switching genes on and off but doesn't change the inheritance.

Take for example those desert frogs (Spadefoot toads,?) whose tadpoles come in two forms. Herbivores and carnivores. They don't get a lot of time with the pools drying up so sometimes the only tadpoles that survive are the ones that turn cannibal to harvest the resources collected by the herbivores. Not too sure if it's like Locusts where overcrowding leads to cannibalism, but IIRC some eggs were larger so those tadpoles had a head start on eating others of their species.

Without the herbivores the cannibals would starve. So while the individual would be better off being a carnivore, the species needs herbivores but they won't make it out of the pond a lot of the time so survivors need to be express both characteristics. You can imagine local selective pressure changing the ratio but you still need both herbivores and cannibals so you won't loss any of the genes.

Labarbapostiza

Capt'n Midnight wrote: »

How does intensive physical exertion influence gene expression ?

Lamarckism was debunked yonks ago.

Isn't there some epigenetic feature that can turn genes on or off between generations?

Yes starvation of pregnant Dutch women at the end of world war II did result in smaller babies but that AFAIK didn't have any genetic component. Yes the children of the daughters were smaller but that was likely to be simply because their ovaries were formed during a term of malnutrition.

I remember the Dutch becoming the tallest people in Europe a few years ago. Nutrition does have a big influence on height.

Speedwell

Yes, of course, there are environmental factors that influence mutations. There's a word for them, "mutagenic". They include, but are not limited to, radiation (including naturally occurring radioactive deposits, radon outgassing, and, oh yeah, sunlight), certain chemicals (naturally occurring and artificial), lack of certain chemicals (i.e. deprivation and malnutrition), certain genetic and disease conditions that can cause gene "fragility" and copying errors, and so forth. But random DNA transcription errors, larger-scale chromosomal abnormalities, and other types of genetic damage do occur naturally and "randomly" (it might be more accurate to say "because of the inherent instabilities of the system").

Not every beneficial mutation is preserved or even expressed, and not every deleterious mutation is fatal. Plenty of mutations have no effect at all. Many mutations that offered a net benefit to a population under environmental stress in the past are liabilities now that the stressor has been removed; sickle-cell anemia for example. Some mutations that confer a benefit also cause problems, such as increased brain size in humans going hand-in-hand with difficult births and extreme neoteny (babies being born, on the whole, "prematurely" compared to the developmental state of other animals at birth). Some of the problems, such as neoteny, turn into benefits in unexpected ways; being born so early developmentally is said to enable us to retain our plasticity of intelligence (we learn better and think better).

One of my friends used to say that it was "suspicious" that the capability to drink milk after the age of weaning arose among herding people. I'm not sure what the problem with that is. That mutation could have arisen several times among people who did not herd and milk animals, but how would we ever know that? Even "beneficial" mutations confer fitness only in appropriate circumstances.

Labarbapostiza

Speedwell wrote: »

One of my friends used to say that it was "suspicious" that the capability to drink milk after the age of weaning arose among herding people. I'm not sure what the problem with that is. That mutation could have arisen several times among people who did not herd and milk animals, but how would we ever know that? Even "beneficial" mutations confer fitness only in appropriate circumstances.

I think lactose intolerance or the suggestion adults are incapable of digesting lactose may not be a thing. Given how much dairy product we consume without much difficulty.

Speedwell

Labarbapostiza wrote: »

I think lactose intolerance or the suggestion adults are incapable of digesting lactose may not be a thing. Given how much dairy product we consume without much difficulty.

"People" is intended to include people outside of the island of Ireland.

Labarbapostiza

Speedwell wrote: »

"People" is intended to include people outside of the island of Ireland.

As I believe, where you find actual lactose intolerance is in the small number of cultures who do not have animal dairy in their diets. They lose the ability to digest lactose, and have a bad reaction to it if they do attempt to digest it. I've heard of African children, brought from regions that very specifically do not have any form of dairy in their diet, and on first contact with a dairy product, they become violently ill. Those groups would be rare, even in Africa. There wouldn't be any specific genetic variation that would make them intolerant of lactose, it's just intolerance through lack of exposure.

There was something I recently heard. Different people react differently to alcohol. It's been a mystery why some people can indulge in chronically high levels of alcohol consumption without deleterious effects, but others can be severely harmed by chronic use of modest amounts that would be well within the recommend maximums. That is people developing life threatening liver disease from drinking a small glass of wine each night. Now, there appear to be hints that it could be due in part to gut bacteria. I wouldn't be surprised if it might be a factor in obesity and similar.

Capt'n Midnight

Labarbapostiza wrote: »

Isn't there some epigenetic feature that can turn genes on or off between generations?

Turning on/off is not the same as changing the genetics.

The genotype is the same but the phenotype is different.

Labarbapostiza

Capt'n Midnight wrote: »

Turning on/off is not the same as changing the genetics.

The genotype is the same but the phenotype is different.

The seed is the same as the plant.

I was listening or watching (or maybe the whole thing was a dream) a documentary on how cuckoos get away with laying their eggs in other birds nests. And what it comes down to is their egg shells can mimic the shell patterns of other birds, but they must lay their eggs in a nest where the pattern is a successful mimic. The victim birds, they have also evolved a protection against this tactic, their shell patterns change to twart the cuckoo. They're able to keep up with each other. If you think of the typical thought on how natural selection works, and randomness. You'd think either the cuckoos would wipe out the cuckholds or the other way around. But they're able to keep up with each other....but there's something very non-random going on in the changes in egg shell pattern of respective birds.

Then again...It might have been a dream.....this whole comment thread could be a dream....it has a dream like quality.

Speedwell

Labarbapostiza wrote: »

As I believe, where you find actual lactose intolerance is in the small number of cultures who do not have animal dairy in their diets. They lose the ability to digest lactose, and have a bad reaction to it if they do attempt to digest it. I've heard of African children, brought from regions that very specifically do not have any form of dairy in their diet, and on first contact with a dairy product, they become violently ill. Those groups would be rare, even in Africa. There wouldn't be any specific genetic variation that would make them intolerant of lactose, it's just intolerance through lack of exposure.

Small number of cultures, such as the majority of Asian populations, the majority of African populations, and the majority of Native American populations? No specific genetic variation, such as the one called primary hypolactasia? Lactose tolerance in non-infants (lactase persistence) developed less than 5,000 years ago in the human population.

Labarbapostiza

Speedwell wrote: »

Small number of cultures, such as the majority of Asian populations, the majority of African populations, and the majority of Native American populations? No specific genetic variation, such as the one called primary hypolactasia? Lactose tolerance in non-infants (lactase persistence) developed less than 5,000 years ago in the human population.

Yeah, well I think it's a spurious claim.

Dairy, is wide spread in Africa. It has been since ancient times. Think of the Masai herders in Kenya. And other parts of Africa have goats and they also still have the ancient mini-cows, that are about the size of a dog. In Africa you would only find small pockets of dairy free environments. In the far east, dairy like yaks are ancient. In India some Hindus consume dairy, and some do not. In south America, where they exist, Llamas are milked. Sometimes dairy is not consumed due to some taboo or misapprehension. My father grew up raising sheep, he thought the idea of consuming sheeps milk was absurd. Even though there were reasons they would milk sheep, they would discard it. In other parts of Europe the use of sheeps milk is very common.

cindyrendy

I think, yes. It may be influenced by the environment.

CramCycle

Capt'n Midnight wrote: »

Yes starvation of pregnant Dutch women at the end of world war II did result in smaller babies but that AFAIK didn't have any genetic component. Yes the children of the daughters were smaller but that was likely to be simply because their ovaries were formed during a term of malnutrition.

Which has also lead to high levels of obesity in a specific generation. Not sure if it is the malnutrition effect but a specific change in the metabolism that has become permanent in that generation (ie conservation) but does not appear to be a selective genetic pressure. Potentially just an on/off switch

Speedwell wrote: »

"People" is intended to include people outside of the island of Ireland.

Lactose intolerance is apparently quite common in Ireland, I was shocked to find this out when I left the confines of the countryside.