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For my first post, I have a kind of dumb/easy question

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

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For my first post, I have a kind of dumb/easy question

Postby IgnorantApe » Sun Jan 16, 2011 3:26 pm

Hey there.

So, I'm sort of new to genetics, and I'm trying to gain a good knowledge of it.
For my first question: I can't seem to wrap my head around the idea of how a single mutation can spread to everyone in the population.

Do I have this right? A mutation pops up in a single individual, who then pops out a few kids with that same mutation, who then pop out more kids with the same mutation, until everyone in the population has it?

But what about everyone else who doesn't have it, do they just die out? What if they had an alternative mutation that was successful?

I hope this doesn't sound too incoherent or stupid. I just want to know how on earth a single individual can cause an allele to go to "fixation". I don't get how a species can be so homogenised.
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Postby Procon1234 » Sun Jan 16, 2011 4:03 pm

Well, some mutations are recessive (and mostly are). So when a person inherits only one allele for that disease, he's just going to be a carrier. In order for that disease to show up, you need both alleles.

Some specific regions do sometimes have a high number of specific diseases. It's mainly because they have a lot people who has that disease, and the chance of the next generation inheriting that same disease is high.

For dominant diseases, they are mostly lethal. They might be infertile or the effects are so bad that the society won't accept them. Those people might not have a next generation to pass on.
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Postby JackBean » Sun Jan 16, 2011 5:54 pm

Procon1234: I don't think you have answered the question

Ape: of course, they do not just die out. However, for every version of an gene (i.e. either mutated or original one) there is a chance of fixation. There can be several ways like gene drafting, bottleneck effect etc.
http://www.biolib.cz/en/main/

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Postby Rap » Sun Jan 23, 2011 7:01 pm

If the mutation is beneficial, then those who have the mutation will do better than those who do not. Every generation, those with the mutation will have more children that reach sexual maturity than those who do not. These children will be more likely to have the mutation than the children of those who do not, and so they too will have more children that reach sexual maturity than those who do not. If you have a case where the population can expand forever, then those with out the mutation do not so much "die out", but rather they get outnumbered or they mate with someone who has the mutation producing children which will tend to have the mutation. Its not so much that those without the mutation die out as it is that they more and more will tend to mate with someone who has the mutation, and their children will carry the mutation.
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Postby JackBean » Tue Jan 25, 2011 7:27 am

however, their children will have only one mutated version and the other will be the original one ;)
http://www.biolib.cz/en/main/

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