mjl1717
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Can anyone explain this law in detail??
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Smell the coffee! "Is That an Osler move??"
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| purplepen
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It is very easy. p and q represent the frequency of two different allels. Don't confuse genotype with phenotype.
I will use some examples here:
Autosomal recessive---------AA, Aa, aa, three different genotype, but only two phenotype, (phenotypically normal, or diseased people, right?), if you use p represent A, q represent a,
then in H-W equation: P^2+2pq+qq^2=1
the gene frequency for AA is pxp=p^2, aa is qxq=q^2, Aa=2pq
In another word, prevalence of homozygous normal is p^2, prevalence of the houmozygous disease is q^2, heterozygous carrier prevalence is 2pq. Here we are talking about phenotype frequency. If the question ask you what is the prevalence of healthy people for this disease, you have to use p^2 +2pq to answer it.
In autosomal dominant: prevalence of disease is calculated through: P^2+2pq, (because AA and Aa are all phenotypically diseased) only q^2 (whose genotype is aa) is disease free.
So it is very easy. AA=p^2 Aa=pq, aa=q^2
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| 99doc
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That was a great way of simplifying things.
I GOT IT INTO MY HEAD,BUDDY.
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| purplepen
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You are welcome 99doc.  I think the Kaplan lecture gave a clear explanation on Genetics. One of the niced, shortest lecture sections. The professor really did a good job. I listened to the lecture twice, read through the book once. And that's it.
One thing I want to add is, in some rare autosomal recessive disease, since q is really a small number, then according to p+q=1, you can just simplify your calculation as p=1, q=whatever the Q stem gives you, and do the calculation from there.
There are some nice, simple Qs here for genetics:
http://medgen.genetics.utah.edu/
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