Which changes first, the genome or the organism?

[OldWiseGuy]

Let's say deer evolved hollow hairs for insulation against the harsh winter cold. Did the change occur in the genome first, or in the hair first. And is there genetic evidence still in the genome of the hair before it evolved?

 

[essentialsaltes]

Let's say deer evolved hollow hairs for insulation against the harsh winter cold. Did the change occur in the genome first, or in the hair first.

In some ways, this represents the difference between Darwin's theory and that of Lamarck, although neither really knew anything about 'genes'. Lamarck thought that characteristics acquired during life could then be passed down to descendants (i.e. hair first, then genes). Whereas Darwin considered that variations in inherited characteristics led to variations in the animals (genes first, then hair).

As we know, Darwin's theory won the day, so the variations in the genome occur first.

And is there genetic evidence still in the genome of the hair before it evolved?

I'm not sure quite what you're asking.

If there was a gene SH (for solid hair) in a deer parent, then if one offspring inherits a mutated form of that gene SH*, that gene might express itself as hollow hair. The parent has SH and solid hair. The offspring has SH* and hollow hair.

Genes are blueprints and bodies are the buildings. So you don't get hollow hair by magic that then gets later boiled down into a blueprint. The gene/blueprint comes first, and then the expression/building comes from it.

 

[OldWiseGuy]

In some ways, this represents the difference between Darwin's theory and that of Lamarck, although neither really knew anything about 'genes'. Lamarck thought that characteristics acquired during life could then be passed down to descendants (i.e. hair first, then genes). Whereas Darwin considered that variations in inherited characteristics led to variations in the animals (genes first, then hair).

As we know, Darwin's theory won the day, so the variations in the genome occur first.



I'm not sure quite what you're asking.

If there was a gene SH (for solid hair) in a deer parent, then if one offspring inherits a mutated form of that gene SH*, that gene might express itself as hollow hair. The parent has SH and solid hair. The offspring has SH* and hollow hair.

Genes are blueprints and bodies are the buildings. So you don't get hollow hair by magic that then gets later boiled down into a blueprint. The gene/blueprint comes first, and then the expression/building comes from it.

But does the new blueprint replace the old, or does the old still hang around somewhere in the genome? What causes genetic/blueprint changes if not stimulus from outside of the genome? Seems like a chicken/egg question.

 

[driewerf]

But does the new blueprint replace the old, or does the old still hang around somewhere in the genome? What causes genetic/blueprint changes if not stimulus from outside of the genome? Seems like a chicken/egg question.

There is no simple answer.
In some cases the genen is a little bit changed, like the substitution of a base pair in a long sequence. in other cases, the "genetic switch" is modified. The "genetic what"? many genes (possibly all) have a kind of switch that is not coded in protein itself, but switches it's gene on and off. These switches react to chemical stimuli like hormones, sugar level etc. In some cases a mutation can cause the switch, the regulatory part of the gene to become more sensitive, and hence the gene will produce more proteins or be active longer.
Another example is gene duplication. At first a mutation causes a double of a gene. When an organism has two copies of a gene the second gene can mutate further without the risk of losing the functionality of the original copy. Sometimes a new functionality can emerge (mostly very closely similar to the first). This can mean that the organism can digest an extra food source and opening extra metabolic pathways.

 

[essentialsaltes]

But does the new blueprint replace the old, or does the old still hang around somewhere in the genome?

dreiwerf's answer about gene duplication is relevant. You might have two copies of a gene. A 'normal' one and a mutant one.

What causes genetic/blueprint changes if not stimulus from outside of the genome?

Mutations.

Maybe a particular example can help. The Lactase gene...

Some population segments exhibit lactase persistence resulting from a mutation that is postulated to have occurred 5,000–10,000 years ago, coinciding with the rise of cattle domestication.[23] This mutation has allowed almost half of the world’s population to metabolize lactose without symptoms. Studies have linked the occurrence of lactase persistence to two different single-nucleotide polymorphisms about 14 and 22 kilobases upstream of the 5’-end of the LPH gene.[24] Both mutations, C→T at position -13910 and G→ A at position -22018, have been independently linked to lactase persistence

So out of the thousands of letters that spell out the lactase gene (or at least the region where it's found), a mutant misspelling at two places allows mutants to drink milk in adulthood, while others are lactose intolerant. So the genes are virtually identical. 99% of the blueprint even for this gene is the same, so to that extent the 'old version' is still there. But it is a slightly misspelled version that provides for different functionality.

 

[Gene2memE]

But does the new blueprint replace the old, or does the old still hang around somewhere in the genome?

Both. Both more the latter than the former. (Hence the prevalence of non-coding DNA in the human genome - depending on the measure used, as little a 1% of our DNA (or as much as about 15%) actively codes the proteins used in our DNA).

It also very much depends on what kind of change in the genome it is though. There are multiple types, insertions, deletions and a couple of types of substitutions.

What causes genetic/blueprint changes if not stimulus from outside of the genome?

Random variation, worked on by natural selection. There are ~150 to 200 changes between mammalian offspring and their parent. Some of these might provide a survival/reproductive success benefit and be conserved for the next generation.

Seems like a chicken/egg question.

Not really.

 

[OldWiseGuy]

Interesting. Thanks all.

 

[FrumiousBandersnatch]

Let's say deer evolved hollow hairs for insulation against the harsh winter cold. Did the change occur in the genome first, or in the hair first. And is there genetic evidence still in the genome of the hair before it evolved?

When a population encounters a change in environment, it may be the case that, due to natural variation, certain individuals are better able to physically (or mentally) adapt to that environment, so those individuals will do better in the new situation (becoming stronger, or faster, or holding their breath longer, finding clever ways to obtain food, etc.) and so out-compete their fellows, being more successful in the reproductive stakes, and passing their adaptable genetics to the next generation. So over time, the mean fitness of the population for the given trait will increase, and without the selective pressure of the old environment, fitness for the old environment will decrease.

So it is possible to have individual adaptation before the population genome 'catches up'.

 

[OldWiseGuy]

When a population encounters a change in environment, it may be the case that, due to natural variation, certain individuals are better able to physically (or mentally) adapt to that environment, so those individuals will do better in the new situation (becoming stronger, or faster, or holding their breath longer, finding clever ways to obtain food, etc.) and so out-compete their fellows, being more successful in the reproductive stakes, and passing their adaptable genetics to the next generation. So over time, the mean fitness of the population for the given trait will increase, and without the selective pressure of the old environment, fitness for the old environment will decrease.

So it is possible to have individual adaptation before the population genome 'catches up'.

It seems that the deer have all caught up, as there are no deer in the northern climes that don't have hollow winter hair.

 

[Ophiolite]

It seems that the deer have all caught up, as there are no deer in the northern climes that don't have hollow winter hair.

Global warming and some suitable mutations may well change that.

 

[Subduction Zone]

Don't get your science from Marvel Comics The X-Men. Mutations are not like that. They tend to be very small changes that would not be noticed if one was not looking for them.

As to how they happen and become part of the genome, the mutations must occur in germ cells for them to be passed on. There are almost endless mutations in your body of various cells.
Most will have no effect at all since most of your DNA is nonfunctioning. And even if a group of cells had a mutation from an early cell to make hollow hair only that small group would make a hollow hair or hollow hairs at best. There would be no way to pass it on.

But if the mutation was in the original cell of an animal it would not only be in every cell of that animal, it would itself be capable of being passed on if the critter bred successfully.

 

[FrumiousBandersnatch]

It seems that the deer have all caught up, as there are no deer in the northern climes that don't have hollow winter hair.

Hollow hair is probably not a trait that is adaptable for individuals, so probably not relevant to the adaptation-precedes-evolution sequence.

 

[Ophiolite]

Don't get your science from Marvel Comics The X-Men. Mutations are not like that. They tend to be very small changes that would not be noticed if one was not looking for them.

As to how they happen and become part of the genome, the mutations must occur in germ cells for them to be passed on. There are almost endless mutations in your body of various cells.
Most will have no effect at all since most of your DNA is nonfunctioning. And even if a group of cells had a mutation from an early cell to make hollow hair only that small group would make a hollow hair or hollow hairs at best. There would be no way to pass it on.

But if the mutation was in the original cell of an animal it would not only be in every cell of that animal, it would itself be capable of being passed on if the critter bred successfully.

Oddly, this appears to have been directed at my previous post, repeated here.

Global warming and some suitable mutations may well change that.

I had not thought it necessary to spell out in detail the concept represented by my summary.
First, may I correct your slightly garbled presentation of the facts:
Mutations in the somatic cells [body] have no effect upon offspring.
Mutations in the germ cells [ova or sperm] do have an effect upon offspring. (You seem to be using the phrase "original cell" rather than the preferred scientific term, germ cell.)

So, mutations are to be found in all germ cells. Almost all possible mutations would be entirely irrelevant to a change from hollow to solid hairs. But, if by chance a suitable mutation occurs then the offspring arising from that mutated germ cell would have solid hairs. In the present environmental conditions this trait would be selected against.

However, if global warming proceeds, environmental conditions change, then hollow hairs would be selected against and if chance had produced a suitable mutation for solid hairs these would be favoured.

That is all captured in the simple sentence "Global warming and some suitable mutations may well change that." I'm sorry if its brevity created ambiguity in your mind.

 

[Subduction Zone]

Oddly, this appears to have been directed at my previous post, repeated here.

I had not thought it necessary to spell out in detail the concept represented by my summary.
First, may I correct your slightly garbled presentation of the facts:
Mutations in the somatic cells [body] have no effect upon offspring.
Mutations in the germ cells [ova or sperm] do have an effect upon offspring. (You seem to be using the phrase "original cell" rather than the preferred scientific term, germ cell.)

So, mutations are to be found in all germ cells. Almost all possible mutations would be entirely irrelevant to a change from hollow to solid hairs. But, if by chance a suitable mutation occurs then the offspring arising from that mutated germ cell would have solid hairs. In the present environmental conditions this trait would be selected against.

However, if global warming proceeds, environmental conditions change, then hollow hairs would be selected against and if chance had produced a suitable mutation for solid hairs these would be favoured.

That is all captured in the simple sentence "Global warming and some suitable mutations may well change that." I'm sorry if its brevity created ambiguity in your mind.

Actually I was responding to @OldWiseGuy . He appeared to have a strange concept of mutations. Perhaps I should have used the quote button.

 

[Ophiolite]

Actually I was responding to @OldWiseGuy . He appeared to have a strange concept of mutations. Perhaps I should have used the quote button.

Great. I was puzzled, but I could see how my very brief observation could have been misinterpreted and I didn't spot the alternative of OWG. Thank you for clarifying.

 

[Tanj]

In some ways, this represents the difference between Darwin's theory and that of Lamarck, although neither really knew anything about 'genes'. Lamarck thought that characteristics acquired during life could then be passed down to descendants (i.e. hair first, then genes). Whereas Darwin considered that variations in inherited characteristics led to variations in the animals (genes first, then hair).

As we know, Darwin's theory won the day, so the variations in the genome occur first.



I'm not sure quite what you're asking.

If there was a gene SH (for solid hair) in a deer parent, then if one offspring inherits a mutated form of that gene SH*, that gene might express itself as hollow hair. The parent has SH and solid hair. The offspring has SH* and hollow hair.

Genes are blueprints and bodies are the buildings. So you don't get hollow hair by magic that then gets later boiled down into a blueprint. The gene/blueprint comes first, and then the expression/building comes from it.

[petpeeve]The genome is a recipe, not a blueprint. Bodies are soufflés, not buildings.[/petpeeve]

 

[essentialsaltes]

[petpeeve]The genome is a recipe, not a blueprint. Bodies are soufflés, not buildings.[/petpeeve]

Maybe you, but I'm built like a brick poophouse.

 

[46AND2]

Maybe you, but I'm built like a brick poophouse.

Hopefully without the stench.

 

[Tanj]

Maybe you, but I'm built like a brick poophouse.

Whereas I collapse in the heat.