Simu text 2019-2020 File Edit Go Tools Help E Section 5. Graded Questions Sickle-Cell Alleles Q NOTES QUESTIONS Q5.1. Which of the following is FALSE? O 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 O 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. O Individuals who are heterozygous HbA/HbS are protected from malaria, and this is why sickle-cell disease persists in wetter, mosquito-prone regions in Africa. 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). Q5.2. 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. All alleles associated with genetic diseases eventually disappear. Submit Q5.3. Someone has handed you the following graph of changes in the frequency of one allele in a population over time. Based on the graph and without any other information, which of the following is most likely true?
The correct answer and explanation is:
To answer the questions provided, I’ll address each one carefully and provide the correct answers with explanations.
Q5.1: Which of the following is FALSE?
Answer:
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).
Explanation:
This statement is false because the heterozygous advantage of HbA/HbS individuals is directly tied to their resistance to malaria. In regions where malaria is absent, there is no selective advantage for being heterozygous, and the normal HbA homozygous individuals are not at a disadvantage. As a result, natural selection would favor individuals with the normal HbA allele since they do not experience the complications associated with carrying one HbS allele. Therefore, the persistence of HbS is unlikely in malaria-free regions.
Q5.2: AFTER malaria is cured, the frequency of the HbS allele should decrease in regions with lots of mosquitoes because:
Answer:
Having one copy of the HbS allele will no longer be advantageous in these regions.
Explanation:
The HbS allele persists in mosquito-prone regions due to the selective advantage it provides to heterozygous individuals (HbA/HbS) in resisting malaria. Once malaria is cured, this advantage disappears, and the HbS allele will no longer be maintained by natural selection. Instead, individuals with homozygous HbS (sickle-cell disease) will continue to face health disadvantages, reducing the allele’s frequency. Over time, the HbS allele will likely decline in frequency, as it no longer provides any adaptive benefit.
Q5.3: Based on the graph of changes in allele frequency, which of the following is most likely true?
Answer and Explanation:
Without a direct view of the graph, it is most likely related to the dynamics of natural selection, genetic drift, or mutation. If the graph shows a gradual decline or stabilization of allele frequency, the explanation might focus on how evolutionary forces (e.g., selection or drift) act on the population. If the graph instead shows an increase in allele frequency, it might suggest positive selection. If you provide more details about the graph, I can refine this explanation further.