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Combination of advantageous mutation

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Combination of advantageous mutation

Postby SheffJoe » Mon May 14, 2012 7:44 pm

If 2 advantageous mutations (A and B) arise in a population, I understand that an individual with A could mate with a B mutant. Some of their offspring could have both mutations. In an example where these 2 mutations lie on the same chromosome at different loci, I understand that through recombination these mutant alleles can be combined onto one chromosome. Thus lots of offspring will have both mutations.

However, what happens when they are on different chromosomes. Recombination cannot bring them together. I know independent assortment could lead to them both being inherited but then they are free to be separated again during meiosis.

Can you tell me where I'm going wrong? Thank you.
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Postby JackBean » Mon May 14, 2012 7:46 pm

Nowhere
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Re:

Postby SheffJoe » Mon May 14, 2012 8:09 pm

JackBean wrote:Nowhere


So advantageous mutations can only be combined when recombination takes place? I just don't understand how those on different chromosomes can ever be combined and "fixed".

For example, if 2 advantageous mutations (A and B) arise in a population, I always just took it for granted that, instead of one out competing the other, they could be combined to form an AB individual. Let's presume they are on different chromosomes. I understand that independent assortment could lead to them both being inherited by it's offspring, but then they can easily be re-separated by independent assortment.
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Postby JackBean » Mon May 14, 2012 8:29 pm

Sure, they can be combined in the meaning that they will be present in one genome. And because they sort independently, the offspring may have only one, both or any of them. But you must understand, that both parents have some probability of having this mutations. And if they are advantageous, their representation in population will be probably high.
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Re:

Postby SheffJoe » Mon May 14, 2012 9:04 pm

JackBean wrote:Sure, they can be combined in the meaning that they will be present in one genome. And because they sort independently, the offspring may have only one, both or any of them. But you must understand, that both parents have some probability of having this mutations. And if they are advantageous, their representation in population will be probably high.


So you're saying that the mutations will spread so much in the population until there will come a point where all possible parents are homozygous for both genes?
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Postby JackBean » Tue May 15, 2012 6:01 am

That doesn't have to be true, because new mutations arise all the time, even the advantageous alleles may mutate into something not-so-advantageous. Thus, there is a chance it will take 100% of the alleles, but probably not (especially in large populations).
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