Hardy-Weinburg Problems

[RHONDAROBINSON]

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Help needed on these two problems. How will I know when to use the p^2+2pq+q^ equation in these two?

1. Hardy-Weinburg law applies to a trait with 2 alleles. The frequency was calculated as being that of 0.3 for recessive allele. What is the frequency of the dominant phenotype? answer=.91

2. If a population has 60% brown eyes, what is the percentage of the recessive allele? answer=36%

Thanks in advance.

 

[UndergradGuy7]

Help needed on these two problems. How will I know when to use the p^2+2pq+q^ equation in these two?

1. Hardy-Weinburg law applies to a trait with 2 alleles. The frequency was calculated as being that of 0.3 for recessive allele. What is the frequency of the dominant phenotype? answer=.91

2. If a population has 60% brown eyes, what is the percentage of the recessive allele? answer=36%

Thanks in advance.

For 1, an allele is p or q depending if its recessive or dominant. If they say that it is a trait, like color, and in this problem it says the trait is determined by two alleles so that means p^2 or q^2.

Anyway it says the recessive allele is 0.3 which is q. If q = 0.3 then the recessive phenotype is 0.3^2 = 0.09

The dominant phenotype is Aa or AA. So it is represented by p^2 + 2pq.
If p+q=1 then p=1-0.3=0.7
then plug it into the equation
(0.7)^2+(2*0.7*0.3)=0.91

 

[CANgnome]

you have the second question worded incorrectly i think.

if dominant phenotype = .6

recessive phenotype = .4 = q2

therefore q = root .4 = .64


p, dominant allele frequency therefore = .36

dominant allele is at 36%

recessive allele at 64%



testing if correct:

plug into equation p2 + 2pq + q2 = 1

0.1296 + .46 + 0.4 = 1

 

[UCB05]

Help needed on these two problems. How will I know when to use the p^2+2pq+q^ equation in these two?

1. Hardy-Weinburg law applies to a trait with 2 alleles. The frequency was calculated as being that of 0.3 for recessive allele. What is the frequency of the dominant phenotype? answer=.91

2. If a population has 60% brown eyes, what is the percentage of the recessive allele? answer=36%

Thanks in advance.

I don't suppose that's a typo in #2? Brown eyes is usually a dominant allele, and using hardy-weinberg assumptions, the recessive color would make up 40% of the population and its allele frequency would be sqrt(.4)=63%

 

[CANgnome]

ignore this post~