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Genetics as it applies to evolution, molecular biology, and medical aspects.

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Mutation

Postby victor » Sat May 07, 2005 12:27 pm

Do you know how many percent possibility of having good mutation from all those mutation that happen to soma cells or gamet cells..? :? .And the second question is which is causing greater loss? is it gene mutation or chromosome mutation??
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Postby thank.darwin » Sun May 08, 2005 4:51 pm

I don't know the exact percent - It is a lot lower than the chance of the mutation being neutral or harmful? Does anyone know an exact number?
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Postby MrMistery » Sun May 08, 2005 5:58 pm

Nobody knows that number because it doesn't exist. How do you know when a mutation is benefical, neutral or harmful? If the organism is better adapted to the environment than it makes more "children" and the gene perpetuates itself-benefical mutation. So, it really depends on the environment. The exact same mutation can be harmful for an organism living in an environment and benefical for an organism of the same species living in another environment.
Example: in the places where malaria lurks at every turn you can detect about 20% has Aa heterozygotus, a being the gene that causes falciform anemia. These individuals have been favoured by evolution cause plasmodium malaria can not live in their blood

If you require more info on this process let me know
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Postby thank.darwin » Mon May 09, 2005 10:07 am

Thanks MrMistery - I had never looked at it that way...
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Postby MrMistery » Wed May 11, 2005 8:08 pm

That's what i'm here for :D :D
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Postby Jelanen » Wed May 11, 2005 9:05 pm

And the chance of a mutation being passed onto offspring is even lower since mutations are recessive and unless the other parent is a carrier or also a mutant, theres a good chance the mutation won't show up in the F1
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Postby canalon » Wed May 11, 2005 9:10 pm

Jelanen wrote:And the chance of a mutation being passed onto offspring is even lower since mutations are recessive and unless the other parent is a carrier or also a mutant, theres a good chance the mutation won't show up in the F1


I have nothing handy to prove that but I think that all mutations are not necessarily recessive. If I remember correctly Sickle cell anemia is due to a mutation and it is co-dominant.
And I totally approve Andrew's answer. Beneficial or harmfull for a mutation depend a lot from the environment.

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Postby Jelanen » Wed May 11, 2005 9:18 pm

I absolutely would not describe sickle cell anemia as a mutation. In malarial parts of the world, being heterozygous confers a greater survival rate than either of the homozygous phenotypes. Both purple and white pea flowers are present in a population, one is dominant over the other, but is the recessive a mutation or just another phenotype? Besides, mutations are generally defined by what came first, so what actually came first....the "normal" or the "abnormal" heme? While I may have slightly mispoke when I said mutations are recessive, it is true that the vast majority of them are recessive.

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Postby canalon » Thu May 12, 2005 1:37 pm

Jelanen wrote:I absolutely would not describe sickle cell anemia as a mutation. In malarial parts of the world, being heterozygous confers a greater survival rate than either of the homozygous phenotypes. Both purple and white pea flowers are present in a population, one is dominant over the other, but is the recessive a mutation or just another phenotype? Besides, mutations are generally defined by what came first, so what actually came first....the "normal" or the "abnormal" heme? While I may have slightly mispoke when I said mutations are recessive, it is true that the vast majority of them are recessive.


Ok the problem is the definition of mutant vs wild type, then. In the Sickle celle anemia I would definitely call the (I hope I'm not wrong) S-Hemoglobin a mutant. Why? Because if it were the wt, I do not think that there would be human beings any more. And I bet that if you compare Hemoglobin and S-hemoglobin to our cousins the apes, you'll see that the S-type would not match (except maybe with a Jaguar... sorry).

Anyway "new phenotypes" can only arise through mutation (in the largest definition: point mutation, horizontal transfer, gene replication,...). And there is no rule wether a mutation should be dominant or recessive or whatever as far as I know. It completely depends on where it happens. A mutation that would cause the over expression of one gene where or when it should be silenced could easily be dominant. As wether it would be benificial or not, as said earler, it completely depends on the environment.

Hope I made my self clear

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Postby Jelanen » Thu May 12, 2005 2:54 pm

Ok, thats it, now I'm gonna have to lay the smackdown. When I get home later tonight (at work atm), I'll break out one of my 3-4 genetics books and start quoting. That will end the recessive mutation thing.

As far as the which is the wild type and which is the mutation, that conversation is effectively over since I don't consider non-human primates my "cousins". Since we aren't going to agree on that point, its not possible for me to argue which is the mutation by following that line of reasoning. I'm going to stay by the claim that SSA isn't as much a mutation as it is an alternative genotype.

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Postby canalon » Thu May 12, 2005 3:23 pm

Ok, thats it, now I'm gonna have to lay the smackdown. When I get home later tonight (at work atm), I'll break out one of my 3-4 genetics books and start quoting. That will end the recessive mutation thing.


Prove me wrong, I'd be delighted. I don't have any genetics textbook at hand, cause I am also in the lab and we deal bacteria, where recessive/dominant are not that common :)
As I said Mutations can be anything (dominant, recessive, co-dominant) depending on where they take place. But I do agree that in a diploid organism, most of the mutations are probably recessive.

As far as the which is the wild type and which is the mutation, that conversation is effectively over since I don't consider non-human primates my "cousins". Since we aren't going to agree on that point, its not possible for me to argue which is the mutation by following that line of reasoning. I'm going to stay by the claim that SSA isn't as much a mutation as it is an alternative genotype.


If you are not conviced that evolution took place, and that apes are related to us, it is indeed imposible to use molecular evolution to prove my point. And since I do not believe that alternative genotypes could have arisen without a mutational event, I think that discussing the matter is pointless. :roll:
But I would still be interested to know what differnec you make between mutation and alternative genotype... Maybe a good starting point for a new thread.

Cheers

Patrick

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Postby Poison » Thu May 12, 2005 6:13 pm

As much as I know, sickle cell anemia is a mutation. A person with sickle cell anemia has the tirplet GTG instead of GAG in the gene for hemoglobin. This base situation causes a valine to replace a glutamic acid in the hemoglobin. So.... Why don't we call this a mutation? :roll:
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