Allele Frequency

[MedPR]

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Why doesn't the allele frequency change when there is non-random mating?

For instance if you have a parent generation of 9 AA individuals and 1 Aa individual. If the 1Aa individual is not allowed to mate, only AA individuals will be produced, thus diluting the frequency of the single "a" allele.

What's going on?

 

[chiddler]

(if i remember correctly)

Allele frequency does change when there is non random mating and random mating.

When it is random, along with the other HW assumptions, it is predictable with the HW equations. When it is non-random, it is less predictable with the model. Either way, there is allele frequency change.

 

[MedPR]

I was told only genotype frequency changes in non-random mating...

 

[chiddler]

better somebody else responds, then. haven't reviewed genetics yet.

 

[MrNeuro]

genotype frequency changes but allele frequency doesn't because w/ non-random mating what happens is you get a decrease in heterozygosity with an increase in homozygosity. the alleles for dominant and recessive that were present in the heterozygotes shift to the homozygote dominants and recessives. Resulting in a change in genotype frequency NOT allele frequency. The reason nonrandom mating is not considered to affect allele frequency per se at this point is because it still has one more step to go before affecting allele frequency and that is natural selection by way of the deleterious effects related to carrying homozygous alleles whether they be dominant or recessive. I believe the term for quantifying this "susceptibility" is fitness.

was that helpful?

 

[MedPR]

genotype frequency changes but allele frequency doesn't because w/ non-random mating what happens is you get a decrease in heterozygosity with an increase in homozygosity. the alleles for dominant and recessive that were present in the heterozygotes shift to the homozygote dominants and recessives. Resulting in a change in genotype frequency NOT allele frequency. The reason nonrandom mating is not considered to affect allele frequency per se at this point is because it still has one more step to go before affecting allele frequency and that is natural selection by way of the deleterious effects related to carrying homozygous alleles whether they be dominant or recessive. I believe the term for quantifying this "susceptibility" is fitness.

was that helpful?

I know the theory behind it, but I don't see it in practice. For instance:

A population of 10 individuals. 9 are homozygous dominant, 1 is homozygous recessive. If you were to prevent the 1 homozygous recessive from mating, only homozygous dominant offspring would be produced and the recessive allele would become more and more diluted, which results in a change in allele frequency within the population. So...?

 

[MrNeuro]

I know the theory behind it, but I don't see it in practice. For instance:

A population of 10 individuals. 9 are homozygous dominant, 1 is homozygous recessive. If you were to prevent the 1 homozygous recessive from mating, only homozygous dominant offspring would be produced and the recessive allele would become more and more diluted, which results in a change in allele frequency within the population. So...?

i think most nonrandom mating relates to its effects on a normal population i can help with that and understanding how genotypes shift while alleles remain constant

in the situation you described above thats natural selection and that DOES affect allele frequencies

non random mating per se doesn't affect allele frequency because its not killing the animals with those alleles its just shifting them. Natural selection is what is getting rid of those alleles.

That help?

 

[MedPR]

i think most nonrandom mating relates to its effects on a normal population i can help with that and understanding how genotypes shift while alleles remain constant

in the situation you described above thats natural selection and that DOES affect allele frequencies

non random mating per se doesn't affect allele frequency because its not killing the animals with those alleles its just shifting them. Natural selection is what is getting rid of those alleles.

That help?

Unfortunately, no 🙁

No "normal" populations are under hardy-weinberg equilibrium, so I'm not sure what you mean in your first sentence.

I understand how natural selection and genetic drift can and probably will change the allele frequency. I'm just not able to see any example where non-random mating will NOT change the allele frequency. If alleles are not allowed to multiple and proliferate at the same rate as other alleles, the allele frequency will change.