Hardy-weinberg problems

[Magus]

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Hey guys,

I keep getting tripped up by hardy weinberg problems in which the question gives a certain percentage of recessives or homozygous dominants or heterozygotes in a population and ask for another percentage i.e. homozyg. dominant, heterozygotes, etc. My problem is not in the actual calculation (p^2 + 2pq + q^2 =1) but rather in the actual understanding of the question.

How do I determine if the percentage or decimal they give me is p^2 or p for instance? Is p just the allelic frequency or some other quantity? Here's an example from one of the kaplan exams:

"If 96% of the individuals in a population have at least one copy of the dominant, "normal" allele as part of their genotype, what percentage of the population will be carriers of the [autosomal recessive] disorder referred to in the passage?"

A good, non-arbitrary way to figure out what exactly they are looking for (either p or p^2) would be most appreciated!

Thanks!

 

[Danny289]

Hey guys,

I keep getting tripped up by hardy weinberg problems in which the question gives a certain percentage of recessives or homozygous dominants or heterozygotes in a population and ask for another percentage i.e. homozyg. dominant, heterozygotes, etc. My problem is not in the actual calculation (p^2 + 2pq + q^2 =1) but rather in the actual understanding of the question.

How do I determine if the percentage or decimal they give me is p^2 or p for instance? Is p just the allelic frequency or some other quantity? Here's an example from one of the kaplan exams:

"If 96% of the individuals in a population have at least one copy of the dominant, "normal" allele as part of their genotype, what percentage of the population will be carriers of the [autosomal recessive] disorder referred to in the passage?"

A good, non-arbitrary way to figure out what exactly they are looking for (either p or p^2) would be most appreciated!

Thanks!

pay attention to this phrase in question: at least one copy
in you equation you have:

p^2 + 2pq + q^2 =1 this question giving information about p^2 + 2pq ( you have two p in p^2 or one p in 2pq ) that is .96 and easy you can find q^2 ====> .96 +q^2= 1===> q^2= .04 ===> q= 0.2
in other hand you have .2 or (20%) rececive allele and .8 or (80%) dominate allele in population(gene pool).
hope it helped 👍

 

[Magus]

thanks, anyone else have a way to solve any h/w problem in a systematic way?

 

[kateoptimistic]

Remember you can also use p+q=1. p is allele 1 and q is allele 2. For example, if a question gives you the frequency of p=0.2, and ask you what is the expected heterozygosity based on HWE.

here is how you do it:
p=0.2--> q=1-p=.8
expected heterozygosity=2pq=2(.2)(.8)=32%
2pq is from the HWE.
this question is similar to the question you posted above, just in a different form.