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Old 05-24-2012
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Genetics Genetics Question from DIT

What is the frequency of the Aa genotype and the AA genotype if the frequency of allele A is 0.9% ?

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My answers were Aa = 0.18 and AA = 0.81.

------------------------------

DIT answers were Aa = 0.095 and AA = 0.9


Can someone explain ?
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Old 05-24-2012
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DIT is wrong?
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Old 05-24-2012
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Going back to the basic equation=

A^2 + 2Aa + a^2= 1

The 0.9 that DIT gave is the frequency of AA already. They basically gave you A^2 from the original equation. Now you have to square root that:
AA= 0.9
A= 0.95

A+a= 1
a= 1-0.95
a= 0.05

2Aa= which is the frequency of the genotype= 2(0.95)(0.05)= 0.095

Hope that helped.

Last edited by islandcrazy; 05-24-2012 at 09:55 PM. Reason: forgot a word :P
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Old 05-24-2012
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I'd say .18 and .81 too. But this will be for a regular AR inheritance.

For x-linked recessive frequency of allele is equal to heterozygous males or something like that... I think here DIT could have talked about that example precisely
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But the question is exactly as stated above =

"What is the frequency of the Aa genotype and the AA genotype if the frequency of allele A is 0.9% ?"

By saying that frequency of allele A = 0.9% ... doesn't that mean that p = 0.9 ?!

Quote:
Originally Posted by islandcrazy View Post
The 0.9 that DIT gave is the frequency of AA already. They basically gave you A^2 from the original equation.
How would you assume that allele A means the genotype AA Or Am I misreading something here ? lol
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Old 05-25-2012
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What section was this in DIT, I think I wrote down some information on how to solve it, but I can't find it.
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Quote:
Originally Posted by islandcrazy View Post
What section was this in DIT, I think I wrote down some information on how to solve it, but I can't find it.
It was in the work book under genetics ... Its in the genetics end session quiz.
Btw your explanation is right. That's how he got the answer but I just don't know how the frequency for Allele A becomes the frequency for genotype AA!
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Quote:
Originally Posted by Hope2Pass View Post
It was in the work book under genetics ... Its in the genetics end session quiz.
Btw your explanation is right. That's how he got the answer but I just don't know how the frequency for Allele A becomes the frequency for genotype AA!
ok,
This is how I always interpret....
if question gives you that the frequency of some allele , here A in this much PERCENTAGE, than I always assume that thet have given A*A...
then work it out and get our a and then 2Aa...

Hope that helped....
you can try this out in practice question...bt dont get too bogged down buddy...
click, smile..and...move on..
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Old 05-25-2012
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i remember this exact question because he pulled random numbers out of his ass

he misread the question, used numbers that werent in the question and hence got a different answer.

both him and you are correct, because you both did different questions.

sometimes he skips questions or misreads them when taking up quizes. its not often but you'll notice it when it happens. this is one such case.
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