A level biology question? (allele frequency) Watch

daytrippper
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Can anyone explain how to work these out? I've got the answers but I don't understand them:

1) In a study of people living in India, the frequency of the IO allele was found to be 0.55 and that of the IA allele, 0.18. What was the frequency of the IB allele in this population?



2) In a village with a population of 500, there were 8 people who were homozygous for the sickle–cell allele and 96 who were heterozygous. Calculate the frequency of the HbS allele in the village. Show your working.
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OxFossil
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(Original post by daytrippper)
Can anyone explain how to work these out? I've got the answers but I don't understand them:

1) In a study of people living in India, the frequency of the IO allele was found to be 0.55 and that of the IA allele, 0.18. What was the frequency of the IB allele in this population?



2) In a village with a population of 500, there were 8 people who were homozygous for the sickle–cell allele and 96 who were heterozygous. Calculate the frequency of the HbS allele in the village. Show your working.
1) The ABO blood group system has only 3 alleles - IA, IB and IO. So the total frequency of these three must add up to 1.0. Adding 0.55 and 0.18 gives you 0.73. Therefore IB frequency = 1.0 - 0.73 = 0.27

2) There are a total of 1000 alleles at this locus in the village population. Homozygous sickle people are SS. Heterozygous are Ss. Everyone else in the village is ss. To find the frequency of S, work out the total number of S alleles present and divide by 1000. So 8 x SS = 16. Add 96 x S = 96 to give a total of 112 S alleles.
112/1000 = 0.112

I hope this is right!
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daytrippper
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(Original post by OxFossil)
1) The ABO blood group system has only 3 alleles - IA, IB and IO. So the total frequency of these three must add up to 1.0. Adding 0.55 and 0.18 gives you 0.73. Therefore IB frequency = 1.0 - 0.73 = 0.27

2) There are a total of 1000 alleles at this locus in the village population. Homozygous sickle people are SS. Heterozygous are Ss. Everyone else in the village is ss. To find the frequency of S, work out the total number of S alleles present and divide by 1000. So 8 x SS = 16. Add 96 x S = 96 to give a total of 112 S alleles.
112/1000 = 0.112

I hope this is right!
ahhh thank you so much!!!!
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