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Author Topic:   What mutations are needed for a particular trait (e.g. wings) to arise?
PaulK
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Posts: 14751
Joined: 01-10-2003
Member Rating: 1.7


Message 61 of 111 (345968)
09-02-2006 5:15 AM
Reply to: Message 48 by skepticfaith
08-31-2006 6:18 PM


Re: Summary ..
What I mean is that there were likely several other mutations that COULD have happened that would have started the development of wings. When discussing probabilities you have to consider not only the outcome that did happen but also those that did not happen but would have been as good.
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jar
Member
Posts: 30934
From: Texas!!
Joined: 04-20-2004


Message 62 of 111 (346016)
09-02-2006 11:25 AM
Reply to: Message 60 by Hawks
09-02-2006 5:00 AM


environment
To predict if a mutation would be beneficial might be more difficult, but given that an often given definition of a mutations is something like "A change in a DNA sequence", I'd like to give an example of a mutation that is highly likely to be beneficial in a certain environment: it is well known that bacteria often acquire resistance to antibiotics via horizontal gene transfer. Thus, a bacterium that has acquired an antibiotic resistance gene (which should fit the definition of a change in DNA sequence) would most likely have acquired a beneficial mutation (assuming that said antibiotic is common in it's environment and that the bacterium was not already resistant).

I agree with that but it brings in the filter, the environment.

What I am perhaps confused about it that we have had folk claim that mutations are "harmful or beneficial or neutral" and that then go on to assert that most mutaions are harmful.

That to me seems unreasonable.

As you mention there can be mutaions that are definitely harmful such as:

Since we know that certain genes are absolutely vital for survival, mutations that render these genes non-functional will by necessity be harmful (to conceive of such a mutation is easy - just delete the entire gene).

In such a case the critter dies, or is not born, or lives a short life and so that mutation simply does not get passed on.

It seems to me then that almost all the other mutations are neutral in and of themselves. If a mutation does not kill the critter or keep it from reproducing then it is neutral until it is filtered by the unique environment. The evironment then and not the mutation is what determines if that particular mutation is harmful or beneficial. Even then, there will be many mutations that are simply not critical as far as the filter is concerned, hair color, eye color, length of eye lashes, heart to the left or heart to the right, four fingers and a thumb or five fingers and a thumb.

All of those neutral mutations just get carried along, making little or no difference, just more or less sitting on the shelf, until some change in the filter, the environment might make them beneficial or harmful.


Aslan is not a Tame Lion
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crashfrog
Inactive Member


Message 63 of 111 (346037)
09-02-2006 1:36 PM
Reply to: Message 60 by Hawks
09-02-2006 5:00 AM


It's time to play...
Beneficial, Neutral, or Harmful!

Suppose that a bacterium recieves a mutation that confers resistance to an antibiotic that is not present in the envrionment. Beneficial or neutral?

Suppose further that the mutation causes resistance by changing a gene product that allows the bacterium to metabolize lactose when glucose is not present. The protein no longer has that function but now promotes resistance against the antibiotic. Neither lactose nor the antibiotic are present in the environment, and glucose is present. Beneficial, neutral, or harmful?

The antibiotic is present, but lactose is not. Beneficial, neutral, or harmful?

Lactose is present, but the antibiotic is not. Beneficial, neutral, or harmful?

Both lactose and the antibiotic are present. Beneficial, neutral, or harmful?

A new antibiotic is introduced that specifically targets the mutation. Wild-type bacteria are not affected. Beneficial, neutral, or harmful?

Edited by crashfrog, : No reason given.


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Archer Opteryx
Member (Idle past 1675 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 64 of 111 (346148)
09-02-2006 11:47 PM
Reply to: Message 63 by crashfrog
09-02-2006 1:36 PM


Re: It's time to play...
Double post. Please excuse.

Edited by Archer Opterix, : Error.


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Archer Opteryx
Member (Idle past 1675 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 65 of 111 (346149)
09-02-2006 11:48 PM
Reply to: Message 63 by crashfrog
09-02-2006 1:36 PM


Re: It's time to play...
[qs]Beneficial, Neutral, or Harmful!
crashfrog[/b]!

Suppose that a bacterium recieves a mutation that confers resistance to an antibiotic that is not present in the environment. Beneficial or neutral?[/qs]

Neutral.

Suppose further that the mutation causes resistance by changing a gene product that allows the bacterium to metabolize lactose when glucose is not present. The protein no longer has that function but now promotes resistance against the antibiotic. Neither lactose nor the antibiotic are present in the environment, and glucose is present. Beneficial, neutral, or harmful?

Um... Neutral.

The antibiotic is present, but lactose is not. Beneficial, neutral, or harmful?

Beneficial. The organism survives.

Lactose is present, but the antibiotic is not. Beneficial, neutral, or harmful?

If glucose still exists: Neutral.
If no glucose: Harmful. Organism loses potential food source.

Both lactose and the antibiotic are present. Beneficial, neutral, or harmful?

If glucose still exists: Beneficial. Resists antibiotic.
If no glucose: Bacterium has bad day.
- First, Beneficial. Resists antibiotic.
- Next, Harmful. Organism starves.

A new antibiotic is introduced that specifically targets the mutation. Wild-type bacteria are not affected. Beneficial, neutral, or harmful?

Harmful. The organism will croak. (No offense.) DOA. Sayonora.

....Do I win?

Edited by Archer Opterix, : Error.

Edited by Archer Opterix, : Restore text.


Archer

All species are transitional.


This message is a reply to:
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NosyNed
Member
Posts: 8838
From: Canada
Joined: 04-04-2003


Message 66 of 111 (346164)
09-03-2006 2:20 AM
Reply to: Message 63 by crashfrog
09-02-2006 1:36 PM


beneficial, neutral or harmful
Actually I read a year or so ago that at least some of the antibiotic resistant mutations are somewhat detrimental (in a competitive sense) to the bacteria carrying them. Makes a bit of sense. A baceria doesn't have a hell of a lot of genome to throw around.

The article suggested that we rotate antibiotics. If you remove one for a few years the non-resistant forms out compete the resistant ones and you "get back" the effectiveness of the antibiotic for another rotation.


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Hawks
Member (Idle past 4224 days)
Posts: 41
Joined: 08-20-2006


Message 67 of 111 (346178)
09-03-2006 6:26 AM
Reply to: Message 62 by jar
09-02-2006 11:25 AM


Re: environment
What I am perhaps confused about it that we have had folk claim that mutations are "harmful or beneficial or neutral" and that then go on to assert that most mutaions are harmful.

Studies have been performed to asses the impact mutations have on the fitness of organisms. Relative to wild-type individuals, fitness in mutants is almost invariably lower. This sort of makes sense, since there are more ways for a protein not to work then there is for it to work (all this assumes that the mutation happens in a sequence that codes for a protein in the first place). Experiments such as these do support the assertion that most mutations are harmful.

The problem with these experiments, as we both would probably agree, is the one of that filter you mentioned. These mutations were harmful in the environment in which they were selected for. They might not have been in another environment. Saying that, even if the environment changed, it would most likely still be true that most mutations are harmful.


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crashfrog
Inactive Member


Message 68 of 111 (346211)
09-03-2006 10:49 AM
Reply to: Message 65 by Archer Opteryx
09-02-2006 11:48 PM


Re: It's time to play...
Well, they were largely rhetorical questions, but-

We have a winner! (Crashfrog, tell him what he's won!)

Um... a cookie?


This message is a reply to:
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nwr
Member
Posts: 5585
From: Geneva, Illinois
Joined: 08-08-2005


Message 69 of 111 (346213)
09-03-2006 10:53 AM
Reply to: Message 68 by crashfrog
09-03-2006 10:49 AM


Re: It's time to play...
Um... a cookie?

For a frog, surely the prize should be a fly or a mosquito :D
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kuresu
Member (Idle past 591 days)
Posts: 2544
From: boulder, colorado
Joined: 03-24-2006


Message 70 of 111 (346295)
09-03-2006 8:44 PM
Reply to: Message 55 by nator
08-31-2006 8:47 PM


Re: Finite possibilities - not infinite..
not cool. way not cool.

I've got blue eyes! And damn it, I'm not gonna let some gov't freaks kill me for it!

(all in jest--but seriously--I'm not letting any one kill me)


All a man's knowledge comes from his experiences
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Archer Opteryx
Member (Idle past 1675 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 71 of 111 (346457)
09-04-2006 2:10 PM
Reply to: Message 68 by crashfrog
09-03-2006 10:49 AM


Re: It's time to play...
crashfrog:

Well, they were largely rhetorical questions

That's OK. They were largely rhetorical answers.

We have a winner!

YAAAAYYYY! I WIN! I WIN!
Oos! Oos! Oos! Oos! Oos!

I was really sweating that. (Humanities major.)

(Crashfrog, tell him what he's won!)

Um... a cookie?

Given our avatars, a dragonfly should suit.
;)

Edited by Archer Opterix, : Punctuation.


Archer

All species are transitional.


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skepticfaith
Member (Idle past 3799 days)
Posts: 71
From: NY, USA
Joined: 08-29-2006


Message 72 of 111 (346469)
09-04-2006 2:46 PM


Other Problems..
quote:
What 'novel traits' are you talking about? What definition of 'novel trait' are you using?

You can take your pick from the development of flight itself (which may have happened from a combination of different things but is still not very clear) to the formation of a wing or even simply the appearance of feathers - they are just elongated scales? How did it get from a scale to a feather?
Now the main problem is that we have not observed ANY such (similar)mutation in higher order animals such as mammals, birds, reptiles etc. That is a mutation that results in a physical change in the animal - a change in the function of a particular limb or organ. (And I dont' mean changes like long to short legs or size differences) - I mean something extraordinary - of this magnitutde - a scale becoming a feather or change in the animal's locomotion ...

Most of the observed 'beneficial' mutations are with bacteria, algae etc..If there anything major as I described above, please provide a link or something - I haven't heard of them.


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arachnophilia
Member (Idle past 55 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 73 of 111 (346482)
09-04-2006 4:09 PM
Reply to: Message 72 by skepticfaith
09-04-2006 2:46 PM


Re: Other Problems..
or even simply the appearance of feathers - they are just elongated scales? How did it get from a scale to a feather?

no, feathers bear more similarity, structurally and chemically, to hair than they do to scales. birds have two types of feathers, the small round reptilian ones (bottom of the foot), and the flat rectangular avian "scutes" (top of the foot). scutes evolved from feathers, not the other way around. there's actually a good selection of dinosaurs specimens with flight feathers on their feet.

Now the main problem is that we have not observed ANY such (similar)mutation in higher order animals such as mammals, birds, reptiles etc.

i'll avoid making a rhetorical point, and contribute something of interest. there's no reason why mammalian hair (as opposed to early archosaur "hair") can't form feathers or scutes. take for example the pangolin, a kind of anteater. they are covered in in overlapping scales that look remarkably like hardened feathers, but are composed of flattened hair. i believe the hair is even soft when they are born -- which means that in the life cycle of a single pangolin we can see hair become something like feathers, which become something like scales.


אָרַח

This message is a reply to:
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Archer Opteryx
Member (Idle past 1675 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 74 of 111 (346507)
09-04-2006 5:27 PM
Reply to: Message 72 by skepticfaith
09-04-2006 2:46 PM


haiku changes = novel traits
skepticfaith:

You can take your pick from the development of flight itself (which may have happened from a combination of different things but is still not very clear)

Bird evolution is still the subject of research but the general direction toward flight is clear enough.

You already have a creature that makes the forearm (flight) stroke of modern birds. It already has forearms covered in feathers that serve as insulation and date bait. It is already small and light and fast. There is no huge step involved for a creature of this sort, when grasping at something and splaying its forearm feathers, to find itself benefiting from lift beneath its wings. If this confers a survival or reproductive advantage--as well it might--subsequent generations will get better at keeping their toes off the ground. And off you go.

even simply the appearance of feathers - they are just elongated scales? How did it get from a scale to a feather?

They are not just elongated scales, as arachnophila observes. A number of mutations is implicated in such a metamorphosis. But that's the essence.

The point is that feathers are not a 'novel' feature in the way you described it earlier: a new organ. Feathers just represent an evolved--mutated--version of a body feature that already existed. A body covering evolved into a body covering.

That is a mutation that results in a physical change in the animal

Yes. Mutations can result in physical changes.

- a change in the function of a particular limb or organ.

Yes. Creatures do find new functions for features they have.

I know a dog that uses his nose to smell, just as his ancestors did 1,000,000 years ago. But he also uses his nose to push his supper dish so that individuals of the species Homo sapiens will get a certain point. This is a nose function unknown to his ancestors. In adapting to a new environment he has found a new function for his nose.

(And I dont' mean changes like long to short legs or size differences)

Intergenerational shifts in size and proportion are unremarkable in terms of genetics and 'odds.' But you can't dismiss them. These are factors that affect function.

Size and weight have a lot to say, for example, about whether a creature--or anything--can get into the air.

T Rex, like the first birds, was a kind of coelurosaur. But it's safe to say that Sue, for all her impressive physical capabilities, would have flown like brick. Wrong size body, wrong size arms.

You admit there is nothing extraordinary about a line of coelurosaurs growing smaller and lighter over succeeding generations as their forelimbs grow longer and quicker. What you don't want to admit is that trends like this are not trivial. In this case the trend in size would be crucial in enabling flight.

- I mean something extraordinary - of this magnitutde - a scale becoming a feather or change in the animal's locomotion ...

You insist on being shown an extraordinary, mega-magnitude evolutionary miracle that defies belief. But nothing extraordinary is called for. Small mutations over succeeding generations, acting in concert with natural selection, can do the job.

Most of the observed 'beneficial' mutations are with bacteria, algae etc..If there anything major as I described above,

There doesn't have to be anything 'major.'

Small mutations over succeeding generations, acting in concert with natural selection, can do the job.

Edited by Archer Opterix, : Quote credit.

Edited by Archer Opterix, : Clarity.

Edited by Archer Opterix, : Typo.

Edited by Archer Opterix, : Typo.


Archer

All species are transitional.


This message is a reply to:
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Hawks
Member (Idle past 4224 days)
Posts: 41
Joined: 08-20-2006


Message 75 of 111 (346546)
09-04-2006 8:17 PM
Reply to: Message 72 by skepticfaith
09-04-2006 2:46 PM


Re: Other Problems..
Now the main problem is that we have not observed ANY such (similar)mutation in higher order animals such as mammals, birds, reptiles etc. That is a mutation that results in a physical change in the animal - a change in the function of a particular limb or organ. (And I dont' mean changes like long to short legs or size differences) - I mean something extraordinary - of this magnitutde - a scale becoming a feather or change in the animal's locomotion ...

If evolution was true, we would not expect to observe extraordinary changes (such as you seem to use the term here). While some mutations might produce some wicked instant new features (such as hens sprouting teeth) this is because the pathways involved in teeth formation are usually swiched off (and also revealing that the ancestors of hens had teeth). Insisting that the observation of extraordinary new feaures have not been done and concluding that this somehow falsifies evolution (if that is what you are doing) is simply a strawman.
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