Hardy Weinberg question

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curious1234
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Hardy Weinberg question

Post by curious1234 » Fri Mar 14, 2008 1:35 am

If you are to estimate frequencies and use Hardy-Weinberg rule to determine proportions of genotypes/phenotypes which method do you use?

I have quantitative information for dominant and recessive traits. Of course, we don't know what the frequency of hetero. traits are.

So, using the information I have I can determine q^2 (recessive) by dividing the recessive individuals by the total # of people. To get q, take the square root and then to get p(dominant) use the 1-q=p equation. To find the frequency of hetero. then do 2pq. To check the values are correct, use the Hardy-Weinberg equation by plugging the values into: p^2 + 2pq + q^2 = 1

OR, I found online another method to determine if the values follow Hardy Weinberg. Using the observed and expected data I can estimate p:
2 X (# observed dominant) + (# observed recessive) / 2 X total individuals. This gives p, so to get q use the 1-p=q equation.

HOWEVER, expected values are then calculated and used in a Chi Square test. No problem getting the expected values ** BUT** what do you use for the observed values when you don't know what the observed heteroz. value is?? When you do the Chi Square, you do the (O-E)^2 / E for p, q and 2pq values but we only really know what the observed values for p and q are?!

How do you do the above calculations when you don't know what the observed heter. value is?

Cat
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Post by Cat » Fri Mar 14, 2008 3:35 am

I would do Punnett squares and Chi square for phenotypes. Hardy-Weinberg equation is best used in population genetics.

curious1234
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Re: Hardy Weinberg question

Post by curious1234 » Fri Mar 14, 2008 4:47 pm

I agree, the Chi square is probably the better option but I don't have values for the heterozygous trait to use. I have only Recessive and Dominant values.

For example, let's say the trait is blue eyes. If 10 people have blue eyes (recessive) and 24 have brown (dominant), how would I do a punnett to get heterozygous individuals? I don't think I can.

Is it even possible to do the calculation with only Recessive and Dominant traits??

Or, is my option just the p^2 + 2pq + q^2 = 1 equation

Cat
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Post by Cat » Fri Mar 14, 2008 5:57 pm

I provided an answer for your question on my web. Please, visit
http://science-ed.fullsubject.com/1-on- ... t11.htm#14

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