[002]
Rottaler
Current Version
Changed line(s) 13 from:
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Selection and migration are not the only forces that can result in changes of gene frequency. There is also mutation (which can in this case be ignored since it is rare) and drift (which can also be ignored for reasons that will now be explained). Drift refers to the effects of random sampling and can result in changes of gene frequency without selection, or even despite selection. Drift is inversely proportional to the size of a population. In very small populations drift is important but its importance decreases precipitously as the population grows. An easy way to see this is to look at an analogy. If you flip 2 coins, it isn’t that unusual to have a result of 100% heads, or 100% tales. If you flip 200 coins, the result is going to be very close to 50% heads and 50% tails. In the same way, if you have two individuals, one of which has a single copy of some variant, and they produce 2 children, it’s very possible that none of the children have a copy. If you have 100 such couples that each produce 2 children, the frequency is going to be about the same next generation. Northern Europe has historically had a small effective population size, but it doesn’t take much to make the effects of drift very small (see above) and in particular, it would be near impossible for a deleterious allele to reach a very high frequency in all but the smallest populations.
to:
Selection and migration are not the only forces that can result in changes of gene frequency. There is also mutation (which can in this case be ignored since it is rare) and drift (which can also be ignored for reasons that will now be explained). Drift refers to the effects of random sampling and can result in changes of gene frequency without selection, or even despite selection. Drift is inversely proportional to the size of a population. In very small populations drift is important but its importance decreases precipitously as the population grows. An easy way to see this is to look at an analogy. If you flip 2 coins, it isn’t that unusual to have a result of 100% heads, or 100% tales. If you flip 200 coins, the result is going to be very close to 50% heads and 50% tails. In the same way, if you have two individuals, one of which has a single copy of some variant, and they produce 2 children, it’s very possible that none of the children have a copy. If you have 100 such couples that each produce 2 children, the frequency is going to be about the same next generation. Northern Europe has historically had a comparatively small effective population size, but it doesn’t take much to make the effects of drift very small (see above) and in particular, it would be near impossible for a deleterious allele to reach a very high frequency in all but the smallest populations.
Changed line(s) 13 from:
n
Selection and migration are not the only forces that can result in changes of gene frequency. There is also mutation (which can in this case be ignored since it is rare) and drift (which can also be ignored for reasons that will now be explained). Drift refers to the effects of random sampling and can result in changes of gene frequency without selection, or even despite selection. Drift is inversely proportional to the size of a population. In very small populations drift is important but its importance decreases precipitously as the population grows. An easy way to see this is to look at an analogy. If you flip 2 coins, it isn’t that unusual to have a result of 100% heads, or 100% tales. If you flip 200 coins, the result is going to be very close to 50% heads and 50% tails. In the same way, if you have two individuals, one of which has a single copy of some variant, and they produce 2 children, it’s very possible that none of the children have a copy. If you have 100 such couples that each produce 2 children, the frequency is going to be about the next generation. Northern Europe has historically had a small effective population size, but it doesn’t take much to make the effects of drift very small (see above) and in particular, it would be near impossible for a deleterious allele to reach a very high frequency in all but the smallest populations.
to:
Selection and migration are not the only forces that can result in changes of gene frequency. There is also mutation (which can in this case be ignored since it is rare) and drift (which can also be ignored for reasons that will now be explained). Drift refers to the effects of random sampling and can result in changes of gene frequency without selection, or even despite selection. Drift is inversely proportional to the size of a population. In very small populations drift is important but its importance decreases precipitously as the population grows. An easy way to see this is to look at an analogy. If you flip 2 coins, it isn’t that unusual to have a result of 100% heads, or 100% tales. If you flip 200 coins, the result is going to be very close to 50% heads and 50% tails. In the same way, if you have two individuals, one of which has a single copy of some variant, and they produce 2 children, it’s very possible that none of the children have a copy. If you have 100 such couples that each produce 2 children, the frequency is going to be about the same next generation. Northern Europe has historically had a small effective population size, but it doesn’t take much to make the effects of drift very small (see above) and in particular, it would be near impossible for a deleterious allele to reach a very high frequency in all but the smallest populations.
