# Hardy-Weinberg equation help needed

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#1
From paper 2, 2018:
10% of the population on the Pacific island of Pingelap are affected by complete achromatopsia (which is caused by an autosomal recessive allele). Use the Hardy-Weinberg equation to calculate the percentage of this population who are heterozygous for this disorder.

q^2 + 2pq + p^2 = 1
p + q = 1

10% = q^2
√0.1 = 0.31 = q
1 - 0.31 = 0.69 = p
0.69^2 = 0.47 = p^2
2pq = 2 x 0.1 x 0.47 = 0.094

Mark scheme says accept answers from 42-44%. Where did I go wrong? Should the 10% be q rather than q^2?
Thanks!
0
3 years ago
#2
You need to use the rest of the information in the question. This is a comprehension question so you must use information from the passage to help you.

It says 1 in 40000 are affected. I would go through the answer but it would be more of an impact if you tried it again using that info.

If you still dont understand, let me know and I will explain it.
(Original post by Kinyonga)
From paper 2, 2018:
10% of the population on the Pacific island of Pingelap are affected by complete achromatopsia (which is caused by an autosomal recessive allele). Use the Hardy-Weinberg equation to calculate the percentage of this population who are heterozygous for this disorder.

q^2 + 2pq + p^2 = 1
p + q = 1

10% = q^2
√0.1 = 0.31 = q
1 - 0.31 = 0.69 = p
0.69^2 = 0.47 = p^2
2pq = 2 x 0.1 x 0.47 = 0.094

Mark scheme says accept answers from 42-44%. Where did I go wrong? Should the 10% be q rather than q^2?
Thanks!
0
#3
(Original post by humble heroics)
You need to use the rest of the information in the question. This is a comprehension question so you must use information from the passage to help you.

It says 1 in 40000 are affected. I would go through the answer but it would be more of an impact if you tried it again using that info.

If you still dont understand, let me know and I will explain it.
I did consider that, but the text says "...with only one in 40 000 being affected. However on the Pacific island of Pingelap ten percent of the population are affected." I assumed the "however" indicates that this is not a situation with one in 40 000 being affected?
0
3 years ago
#4
Ahh, no it means that of the 40,000 that inhabit the island, 10% of the 40,000 (hence 4000) are affected.

That means you can work out the genotype frequency of affected individuals (q^2). 4000/40000
(Original post by Kinyonga)
I did consider that, but the text says "...with only one in 40 000 being affected. However on the Pacific island of Pingelap ten percent of the population are affected." I assumed the "however" indicates that this is not a situation with one in 40 000 being affected?
0
3 years ago
#5
Hey, you made a very minor mistake when calculating the final result.
You seem to have used p^2(0.47) instead of p(0.69) and q^2(0.1) instead of q(0.31) in 2*p*q. So 2*q^2*p^2. If you calculate 2 * 0.31 * 0.69 the result is 0,4278 which is correct.
1
3 years ago
#6
yes
(Original post by Lintar)
Hey, you made a very minor mistake when calculating the final result.
You seem to have used p^2(0.47) instead of p(0.69) and q^2(0.1) instead of q(0.31) in 2*p*q. So 2*q^2*p^2. If you calculate 2 * 0.31 * 0.69 the result is 0,4278 which is correct.
0
#7
(Original post by Lintar)
Hey, you made a very minor mistake when calculating the final result.
You seem to have used p^2(0.47) instead of p(0.69) and q^2(0.1) instead of q(0.31) in 2*p*q. So 2*q^2*p^2. If you calculate 2 * 0.31 * 0.69 the result is 0,4278 which is correct.
How stupid of me! Thanks for clearing that up!!
0
3 years ago
#8

Watch here, all explained
(Original post by Kinyonga)
From paper 2, 2018:
10% of the population on the Pacific island of Pingelap are affected by complete achromatopsia (which is caused by an autosomal recessive allele). Use the Hardy-Weinberg equation to calculate the percentage of this population who are heterozygous for this disorder.

q^2 + 2pq + p^2 = 1
p + q = 1

10% = q^2
√0.1 = 0.31 = q
1 - 0.31 = 0.69 = p
0.69^2 = 0.47 = p^2
2pq = 2 x 0.1 x 0.47 = 0.094

Mark scheme says accept answers from 42-44%. Where did I go wrong? Should the 10% be q rather than q^2?
Thanks!
1
1 year ago
#9
(Original post by Kinyonga)
From paper 2, 2018:
10% of the population on the Pacific island of Pingelap are affected by complete achromatopsia (which is caused by an autosomal recessive allele). Use the Hardy-Weinberg equation to calculate the percentage of this population who are heterozygous for this disorder.

q^2 + 2pq + p^2 = 1
p + q = 1

10% = q^2
√0.1 = 0.31 = q
1 - 0.31 = 0.69 = p
0.69^2 = 0.47 = p^2
2pq = 2 x 0.1 x 0.47 = 0.094

Mark scheme says accept answers from 42-44%. Where did I go wrong? Should the 10% be q rather than q^2?
Thanks!
I done
q^2 = 0.1 so q=0.316
1-0.316= 0.684
P=0.684
2 x 0.316 x 0.684 = 0.43
0.43 x100= 43%

1st equation- p+q=1
2nd equation - 2 x p x q (heterozygous)
0
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