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Author Topic:   The dilution of the effects of genetic mutation.
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


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 Sickle cell trait - Wikipedia
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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we are limited in our ability to understand
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This message is a reply to:
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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


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:
ADW: Artiodactyla: INFORMATION
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.
Ungulate - Wikipedia
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
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Rebel American Zen Deist
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This message is a reply to:
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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 16 of 18 (522564)
09-04-2009 12:28 AM
Reply to: Message 12 by AndrewPD
09-03-2009 6:55 PM


zebras and stripes
Hi AndrewPD, welcome to the fray.
I'm suprised anything has survived this long.
Fortunately, reality is unaffected by your opinion.
And Why would a zebra without the stripes not survive also?
They have.
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.
Google "neutral mutation" -- you are correct.
Would a striking feature such as the zebra's black and white stripes have occured in one mutation?
Does it need to?
Equus - Wikipedia(genus)
quote:
Quagga (now extinct)
Enjoy.
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we are limited in our ability to understand
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Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
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This message is a reply to:
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