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ID: 65051 • Letter: T
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These questions will be graded by your instructor. The answers wil be displayed after all students have completed the module. Click Submit All at the bottom of the page to turn in your answers. Which of the following is NOT true? If a genetic disease reduces fertility and the allele that causes the disease offers no other advantage, the allele will likely eventually disappear, due to natural selection. Natural selection does not favor individuals who are homozygous for the sickle-cell allele, because these individuals typically die before they are old enough to reproduce. Individuals who are heterozygous HbA/HbS are protected from malaria, and this is why sickle-cell In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HbA). AFTER malaria is cured, the frequency of the HbS allele should decrease in regions with lots of mosquitoes because: People will no longer die from sickle-cell disease in these regions. Having one copy of the HbS allele will no longer be advantageous in these regions. Natural selection will no longer act on the HbS allele at all in these regions.Explanation / Answer
Q.49 Correct answer is:In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a fitness advantage over those who are homozygous for the normal hemoglobin allele (HbA).
Reason: People who live in malaria affected areas can have benefit if they are heterozygous for sickle cell anaemia because the heterozygous condition provides resistance to people against malaria.If there occurs malaria in that region, there will be no benefit of heterozygous HbA/HbS alleles.
Q.50 Correct answer is:Having one copy of the HbS allele will no longer be advantageous in these regions.
Reason:Sickle cell disease is expressed in a homozygous recessive condition and offers resistance against malaria when expressed in heterozygous condition.After malaria is cured there will be no requirement of HbS allele and its frequency will therefore decrease.
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