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Author Topic:   The dilution of the effects of genetic mutation.
AndrewPD
Member (Idle past 494 days)
Posts: 133
From: Bristol
Joined: 07-23-2009


Message 1 of 18 (516096)
07-23-2009 11:52 AM


what prevents genetic mutations from been instantly diluted when occuring in a single representative of a species?

Does the same genetic mutation occur several times across the board in a species. Or does the one gene carrier have to reproduce numerous times?

And how does the mutated gene survive the reproduction process if the mutation provides an incompatible feature?

For instance if I developed the ability to withstand malaria but only had one child and that child only had a couple of offspring when does the feature become a predominant one across a whole species?
If all cows have have hooves than that feature was some how shared widely to create a new species with millions of members that all reproduce compatibly.


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Adminnemooseus
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Message 2 of 18 (516181)
07-23-2009 8:20 PM


Thread Copied from Proposed New Topics Forum
Thread copied here from the The dilution of the effects of genetic mutation. thread in the Biological Evolution forum.
    
RAZD
Member
Posts: 19758
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.8


Message 3 of 18 (516186)
07-23-2009 9:03 PM
Reply to: Message 1 by AndrewPD
07-23-2009 11:52 AM


quantum mutations
Hi AndrewPD, and welcome to the fray.

what prevents genetic mutations from been instantly diluted when occuring in a single representative of a species?

You can think of mutations as digital or quantum effects - the offspring either inherit the mutation or they don't. The average probablity is 50:50 that it will be passed\not passed.

Does the same genetic mutation occur several times across the board in a species. Or does the one gene carrier have to reproduce numerous times?

The latter is the case. When the mutation offers a distinct advantage for survival or reproduction then it is likely to be passed to more offspring. The question that comes up then is what about the descendants of others that survive and reproduce without the mutation -- how are they affected?

What is interesting is that populations tend to mix back and forth a lot and every time a mutant carrier mates with a non-mutant carrier there is a mixing of each genetic lineage. It doesn't take too many generations in a fixed size population before normal breeding of mating individuals results is a rather complete mixture.

And how does the mutated gene survive the reproduction process if the mutation provides an incompatible feature?

Many mutations are neutral - offer no benefit one way or the other, and obviously do not affect the transmission of the mutation by reproduction with others. What often happens with mildly deleterious mutations is that they "piggyback" on genes with strong positive selection, and are carried into the next generation in spite of having adverse effects.

For instance if I developed the ability to withstand malaria but only had one child and that child only had a couple of offspring when does the feature become a predominant one across a whole species?

When there is a malaria epidemic that wipes out everyone without the mutation. It can also happen when the epidemic wipes out all males without the mutation.

Curiously, sickle cell anemia is just such a mutation, except for an added twist: if you inherit copies of the mutation from both parents you die. This may seem like a sure way to eliminate the mutation, but consider that anyone with ONE copy survives malaria, anyone with NO copies dies of malaria, and anyone with BOTH copies dies of the mutation. Without the mutation all die, but with the mutation in the population, only 1/2 die.

See http://en.wikipedia.org/wiki/Sickle_cell_trait

If all cows have have hooves than that feature was some how shared widely to create a new species with millions of members that all reproduce compatibly.

Look up even toed ungulates and odd toed ungulates.

Enjoy.

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lyx2no
Member (Idle past 2795 days)
Posts: 1277
From: A vast, undifferentiated plane.
Joined: 02-28-2008


Message 4 of 18 (516188)
07-23-2009 9:28 PM
Reply to: Message 1 by AndrewPD
07-23-2009 11:52 AM


Howdy
what prevents genetic mutations from been instantly diluted when occuring in a single representative of a species?
Nothing… nothing at all. The mutation is instantly diluted. If it's dreadfully deleterious it won't go far. If it's basically neutral it will spread or fail on the coattails of the organism's offspring. If it's exceptionally beneficial it will spread far and wide relative to its effect. Neutral if the likely case. Then half the kids will get it; the other half won't. A quarter of the grandkids, and an eighth of he great-grandkids. Somewhere along the line the greatn-grandkids will mate with each other. Then we get to see how it acts in pairs. Same rules as before but surer.

Does the same genetic mutation occur several times across the board in a species. Or does the one gene carrier have to reproduce numerous times?
Nope… just the once. The mutation is a completely random event.

And how does the mutated gene survive the reproduction process if the mutation provides an incompatible feature?
For the most part this is a misconception of how organisms evolve. Mutations don't produce whole parts except possibly on the smallest scale: someone other than I would have to address that. Arms, hands and finger were gradually modified from fins. One can look at the structure of the bony fishes and see the similarities. Fins were modifications of nubbins on the sides of worm like creatures.

There are groups of genes that cause other groups of genes to turn on and off. Look at Millipedes. If their gene for body segments clicked on a few extra times do you think they'd notice?

For instance if I developed the ability to withstand malaria but only had one child and that child only had a couple of offspring when does the feature become a predominant one across a whole species?
If all cows have have hooves than that feature was some how shared widely to create a new species with millions of members that all reproduce compatibly.

Very likely genes for wonderful things come and go every day. I took out a squirrel with a BB gun earlier this week whose offspring, 20 million years hence would have held our degenerate human descendants as chattel.

No need to thank me.


Ridicule is the only weapon which can be used against unintelligible propositions. Ideas must be distinct before reason can act upon them.
— Thomas Jefferson

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Dr Adequate
Member
Posts: 16085
Joined: 07-20-2006
Member Rating: 10.0


Message 5 of 18 (516193)
07-23-2009 11:59 PM
Reply to: Message 1 by AndrewPD
07-23-2009 11:52 AM


what prevents genetic mutations from been instantly diluted when occuring in a single representative of a species?

"Diluted" is not the right word.

A (diploid) organism will have 0, 1 or 2 copies of a given allele.

When a new mutation arises, you have one member of the gene pool with one copy.

Now this can't be "diluted", as such, because the only whole number smaller than 1 is 0.

Of course, it can fall to 0. Even if the mutation is a very good one, a tree could fall on its carrier or something, C'est la vie.

Does the same genetic mutation occur several times across the board in a species. Or does the one gene carrier have to reproduce numerous times?

That depends ... I have seen it said that when the rat poison warfarin was introduced, similar mutations against it emerged and then were selected for in different places. And, since mutations are random, we may presume that such mutations had been cropping up in rats since first there were rats, but were never selected for because there wasn't any warfarin.

Of course with rats you have a large geographically widespread species. In a smaller population in a smaller area, it would be more likely that a successful mutation would start in one individual and spread through the population before it could occur a second time.

And how does the mutated gene survive the reproduction process if the mutation provides an incompatible feature?

I'm not quite sure what you're getting at --- if by "an incompatible feature", you mean something that makes the net effect of the mutation harmful, then (except by some wild fluke) it would be eliminated by selection.

For instance if I developed the ability to withstand malaria but only had one child and that child only had a couple of offspring when does the feature become a predominant one across a whole species?

Well, it wouldn't be selected for at all unless there was malaria where you live.

So suppose there is. But this still leaves an element of chance, because there are lots of other things that can kill you and your offspring. There's always this element of chance --- it's called genetic drift --- it's natural selection's idiot kid brother. A mutation is particularly vulnerable to this, of course, when it has only a few carriers, as in the scenario you describe.

In fact, if you do the math, most beneficial mutations will go extinct in the population despite their benefits. So it's a good thing that there are plenty of them (genes for warfarin resistance in rats, for example, must have been produced by mutation more often than they succeeded in spreading through the gene pool).

If all cows have have hooves than that feature was some how shared widely to create a new species with millions of members that all reproduce compatibly.

Well, hooves aren't an all-or-nothing feature, as you can see by studying the well-documented evolution of the horse. The central toe got bigger, the outer toes became smaller, then vestigial, then vanished.

I don't quite see how this fits with your other questions.

---

P.S: Welcome to the forum.

Edited by Dr Adequate, : No reason given.


This message is a reply to:
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Replies to this message:
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AndrewPD
Member (Idle past 494 days)
Posts: 133
From: Bristol
Joined: 07-23-2009


Message 6 of 18 (516518)
07-25-2009 7:40 PM
Reply to: Message 5 by Dr Adequate
07-23-2009 11:59 PM


If all cows have have hooves than that feature was some how shared widely to create a new species with millions of members that all reproduce compatibly.

Well, hooves aren't an all-or-nothing feature, as you can see by studying the well-documented evolution of the horse. The central toe got bigger, the outer toes became smaller, then vestigial, then vanished.

I will try an elaborate on what I meant.

If there are a million black and white dairy cows with hooves do they all originate from one original cow like creature that had a specific set of mutations to create the current appearance of the dairy cow?

For instance if I had a baby that had green skin that trait could only be passed on through his offspring.

Therefore doesn't that mean that every species can only descend from one pair? Unless two identical species can evolve alongside one another. Unless I'm missing the point somewhere.

My essential point though is that it seems hard for a genetic mutation happening in isolation in one organism could become a widespread feature. Unless there were lots on inbreeding.


This message is a reply to:
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Blue Jay
Member (Idle past 777 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 7 of 18 (516520)
07-25-2009 8:30 PM
Reply to: Message 6 by AndrewPD
07-25-2009 7:40 PM


It's time for a wacky example!
Hi, Andrew.

Welcome to EvC!

AndrewPD writes:

Therefore doesn't that mean that every species can only descend from one pair? Unless two identical species can evolve alongside one another. Unless I'm missing the point somewhere.

Yes, you're missing something.

Every pair of people comes from two pairs of other people, right?

So, your green-skinned kid came from one pair (you and your spouse), and your green-skinned kid's future spouse came from another pair. In turn, each of those four people came from another pair, each of whom also came from another pair.

Now, let's say I have a kid with pointy ears, like Spock. If my kid married your kid, they could have a pointy-eared, green-skinned baby. One trait came from your side, and one trait came from my side. The grandkid looks weird, but she is not a new species.

Then, let's say Dr Adequate's kid has six fingers. Somewhere along the line, one of his kid's descendants marries one of our pointy-eared, green-skinned grandkid's descendants, and we now have a six-fingered, pointy-eared, green-skinned person whose unique traits are traceable to three different original pairs.

Eventually, RAZD's and lyx2no's lineages get mixed in, etc., and the descendant has a fat nose, groucho eyebrows, vampire fangs, retractable fingernails, X-ray vision, six fingers, pointy ears and green skin. And, finally, they lose the ability to breed with normal humans, thus making them a new species.

So, just because one mutation comes from one pair, doesn't mean that the entirety of the species' genome comes from that one pair. Those traits accumulated from multiple pairs during a time when the carrier of the unique mutation could still interbreed with the "normal" population.

Edited by Bluejay, : "form" and "from" are not interchangeable


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


This message is a reply to:
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RAZD
Member
Posts: 19758
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.8


Message 8 of 18 (516521)
07-25-2009 8:34 PM
Reply to: Message 6 by AndrewPD
07-25-2009 7:40 PM


Simple misconceptions
Hi AndrewPD, welcome back

For instance if I had a baby that had green skin that trait could only be passed on through his offspring.

Therefore doesn't that mean that every species can only descend from one pair? Unless two identical species can evolve alongside one another. Unless I'm missing the point somewhere.

What would prevent your baby from breeding with other humans? Would you not agree that skin color, while unusual, would not necessarily make breeding with other humans incompatible. Green skin alone is not enough to cause speciation -- and what you are really asking is how a new species arises if you need breeding pairs.

You may be familiar with basic genetics of reproduction:

               father's x     fathers's y
mother's x child xx child xy
mother's x child xx child xy

offspring are female male

If this is a brand new mutation, your child with the green skin would gotten the mutation from one of it's parents, it would be heterozygous, with one g (green) and and one n (not green) gene, with similar results:

               father's n     fathers's g
mother's n child nn child gn
mother's n child nn child gn

offspring are not green green

So only two out of four of your child's offspring - on average - would carry the green gene.

Thus there would be mixed green and not green individuals within the breeding population.

If there later was a situation where the population split, and one daughter population lived where there was a selective advantage for green skin (say in a jungle where it was good camouflage), then it would eventually predominate in that population. If the other daughter population lived where there was a selective advantage to not green skin (say in a desert, where it was a disadvantage), then not-green would eventually predominate in that population.

This would not prevent the two populations from interbreeding in any overlapped habitats (hybrid zones), however the selective pressures in each population over time would add other mutations to the mix in each individual population that were not shared or selected against in the other populations, over time such additional mutations can make the populations incapable of interbreeding.

More likely is that they will soon not see the other population individuals as potential mates and just cease interbreeding even when capable.

Thus after many generations of populations full of breeding individuals, we eventually end up with one population that is green skinned and one that is not.

If there are a million black and white dairy cows with hooves do they all originate from one original cow like creature that had a specific set of mutations to create the current appearance of the dairy cow?

Along with the billions of non-black and white cows, ... who also are descendants of some ancestral even toed mammal, like antelopes and deer, ... and hippos, that also have split hooves, and which are also even toed ungulates:

http://animaldiversity.ummz.umich.edu/site/accounts/information/Artiodactyla.html

quote:
The artiodactyls are a large and remarkably diverse group of mammals, containing around 220 living species placed in 10 families. The majority live in relatively open habitats, such as plains and savannas, but others dwell in forests, and one group is semiaquatic. Within the order can be found some of the fastest-running mammals, but the Artiodactyla also includes relatively slow and cumbersome species such as pigs and hippos.

Artiodactyls are paraxonic, that is, the plane of symmetry of each foot passes between the third and fourth digits. In all species the number of digits is reduced at least by the loss of the first digit, and the second and fifth digits are small in many. The third and fourth digits, however, remain large and bear weight in all artiodactyls. This pattern has earned them their name, Artiodactyla, which means "even-toed." Artiodactyls stand in contrast to the "odd-toed ungulates," the Perissodactyla, in which the plane of symmetry runs down the third toe.


As I suggested previously, there are two basic groups of ungulates, even-toed and odd-toed, where ungulates are hooved animals. A common odd-toed ungulate is the horse.

http://en.wikipedia.org/wiki/Ungulate

quote:
Ungulates (meaning roughly "being pawed" or "hoofed animal") are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving.

Enjoy.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

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Dr Adequate
Member
Posts: 16085
Joined: 07-20-2006
Member Rating: 10.0


Message 9 of 18 (516530)
07-25-2009 10:31 PM
Reply to: Message 6 by AndrewPD
07-25-2009 7:40 PM


Unless I'm missing the point somewhere.

You seem to be missing a few points.

One mutation doesn't make a new species. Or if it ever did, then that new species would start off consisting of one individual unable to mate with the old species (by definition of species) so it would be an evolutionary dead end.

Rather, what turns one species into another is an accumulation of changes over generations.

Here's an analogy: I speak the same language as my parents, who speak the same language as their parents, who spoke the same language as their parents, and so forth. And yet if you go a thousand years back you find that my ancestors spoke Anglo-Saxon, which looks like this:

Fęder ure, šu še eart on heofonum, si šin nama gehalgod. To becume šin rice; gewurde šin willa on eoržan swa swa on heofonum. Urne dęgwhamlican hlaf syle us todęg, and forgyf us ure gyltas, swa swa we forgyfaž urum gyltendum. And ne gelęd šu us on costnunge, ac alys us of yfele. Sožlice.

(If I tell you that this is the Lord's Prayer, and that š and ž are how they wrote "th", then you may see some relationships with Modern English.)

Now, this is a different language from Modern English. And yet there was never a point at which one person started speaking a brand new language, comprehensible only to his children whom he raised speaking this new language. At every point, people's language was comprehensible to their neighbors, their parents, their children ... and yet by progressive small changes, we ended up with a different language.

The normal process of speciation is like that. It doesn't happen by one big jump producing incompatibility.

Edited by Dr Adequate, : No reason given.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member
Posts: 16085
Joined: 07-20-2006
Member Rating: 10.0


Message 10 of 18 (516534)
07-25-2009 10:38 PM
Reply to: Message 7 by Blue Jay
07-25-2009 8:30 PM


Re: It's time for a wacky example!
Now, let's say I have a kid with pointy ears, like Spock. If my kid married your kid, they could have a pointy-eared, green-skinned baby. One trait came from your side, and one trait came from my side. The grandkid looks weird, but she is not a new species.

Then, let's say Dr Adequate's kid has six fingers. Somewhere along the line, one of his kid's descendants marries one of our pointy-eared, green-skinned grandkid's descendants, and we now have a six-fingered, pointy-eared, green-skinned person whose unique traits are traceable to three different original pairs.

Eventually, RAZD's and lyx2no's lineages get mixed in, etc., and the descendant has a fat nose, groucho eyebrows, vampire fangs, retractable fingernails, X-ray vision, six fingers, pointy ears and green skin. And, finally, they lose the ability to breed with normal humans, thus making them a new species.

This is slightly misleading, because it suggests a situation where all the genetic material for a new species is present in one generation just waiting for recombination to assemble it into a new species. Which is not what happens.


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Blue Jay
Member (Idle past 777 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 11 of 18 (516628)
07-26-2009 2:20 PM
Reply to: Message 10 by Dr Adequate
07-25-2009 10:38 PM


Re: It's time for a wacky example!
Hi, Dr Adequate.

Dr A writes:

This is slightly misleading, because it suggests a situation where all the genetic material for a new species is present in one generation just waiting for recombination to assemble it into a new species.

Well, it wasn't meant to be an analogy for the entire concept of evolution: it was meant to be an explanation for how mutations from different sources contribute to an individual's genome.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


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AndrewPD
Member (Idle past 494 days)
Posts: 133
From: Bristol
Joined: 07-23-2009


Message 12 of 18 (522516)
09-03-2009 6:55 PM


Would a striking feature such as the zebra's black and white stripes have occured in one mutation?

And Why would a zebra without the stripes not survive also?

I get the impression that any feature that survives is attributed to fitness but it seems that any trait that survives is not intending to survive so could have survived simply because it didn't have a negative effect.

otherwise you'd imagine we'd all be super fit and not prone to drop dead from and infection or starve.

I'm suprised anything has survived this long.


Replies to this message:
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themasterdebator
Inactive Member


Message 13 of 18 (522521)
09-03-2009 7:08 PM
Reply to: Message 12 by AndrewPD
09-03-2009 6:55 PM


Hi, Andrew welcome to the forums.

there is a school of thought which believes that many mutations that happen are not harmful or beneficial, they are neutral or extremely close to neutral. This may have lead to increased speciation, as a large number of neutral mutations may cause one population to not mate with another population.

However, Zebra stripes are actually beneficial. A simple google search of the term "benefits of zebra stripes" pulls up this article ( http://animals.howstuffworks.com/mammals/question454.htm ) which explains that zebra stripes are effective camouflage against savanna predators and works well for confusing them when zebras travel in large groups. They are also useful for finding mates.

I understand you are new here, so I will give you some advice. I recommend you do a little research on something before asking questions(A simple google search would suffice), that way you don't end up making false claims and can make a much clearer post.


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AndrewPD
Member (Idle past 494 days)
Posts: 133
From: Bristol
Joined: 07-23-2009


Message 14 of 18 (522528)
09-03-2009 9:11 PM
Reply to: Message 13 by themasterdebator
09-03-2009 7:08 PM


This is from wiki.;http://en.wikipedia.org/wiki/Zebra

quote:
A herd of zebras scattering to avoid a predator will also represent to that predator a confused mass of vertical stripes travelling in multiple directions making it difficult for the predator to track an individual visually as it separates from its herdmates, "although biologists have never observed lions appearing confused by zebra stripes."

A more recent theory, supported by experiment, posits that the disruptive colouration is also an effective means of confusing the visual system of the blood-sucking tsetse fly.[5] Alternative theories include that the stripes coincide with fat patterning beneath the skin, serving as a thermoregulatory mechanism for the zebra, and that wounds sustained disrupt the striping pattern to clearly indicate the fitness of the animal to potential mates.


If the stripes were effective when there was a mass of Zebras together then just one Zebra becoming striped would have stood out like a sore thumb.

But my question is at what stage did the current Zebra become what it is? What was wrong with all the species that led up to the eventual Zebra?


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Coyote
Member (Idle past 185 days)
Posts: 6117
Joined: 01-12-2008


Message 15 of 18 (522538)
09-03-2009 9:38 PM
Reply to: Message 14 by AndrewPD
09-03-2009 9:11 PM


Zebras, and evolution
If the stripes were effective when there was a mass of Zebras together then just one Zebra becoming striped would have stood out like a sore thumb.

It is a creationist myth that evolution happens in giant leaps, for example a lizard to a bird or a zebra with absolutely no stripes to a fully striped one. Along these same lines, we often see the argument from creationists that an individual in a population who happens to have such an extreme mutation will have nobody to mate with. This is supposed to be a telling argument against evolution.

It might be if evolution proposed such a thing. Rather, evolution occurs in tiny steps, with favorable mutations often spreading through a population over time. No giant leaps.

But my question is at what stage did the current Zebra become what it is? What was wrong with all the species that led up to the eventual Zebra?

The earlier species of zebra might have been well adapted to their environment (including predators). Subsequent populations and species were perhaps just a little bit better adapted due to mutations and natural selection. Over time these changes amounted to new species, but if you were there at the time you would likely see no change from generation to generation.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
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