Q5.1. Which of the following is FALSE? 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 disease persists in wetter, mosquito-prone regions in Africa. In regions where malaria does not occur, individuals who are heterozy gous 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 $ 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. 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 allele does not offer any fitness advantage and the population is small. The allele does not offer any fitness advantage and the population is large. The allele offers a selective advantage and the population is small. The allele was introduced at a very low frequency and the population is large. Q5.4. If the frequency of the HbS allele is 0.2 in a population, what is the frequency of the H b A allele (assuming this is a two-allele system)? Q5.5. Which of the following would be sufficient for the Hardy-Weinberg equation to accurately predict genotype frequencies from allele frequencies? p + q = 1 The population is not evolving due to natural selection. The population is not evolving due to any of the conditions that distupt Hardy-Weinberg equilibrium. The population is infinitely large. Q5.6. In a population, if the proportion of individuals who have sickle-cell disease is 0.40 , and the population is assumed to be at Hardy-Weinberg equilibrium, what is the expected frequency of the HbS allele? (Hint: What is the genotype of people with sickle-cell disease, and how is that genotype represented in the Hardy-Weinberg equation?) Use the following additional passage to answer the next question. Suppose you travel to the future, to a time when neither cystic fibrosis nor tuberculosis have caused any deaths for many generations. In all of these future populations, the cystic fibrosis allele still exists at a low frequency. Q5.10. You visit a huge city with millions of people. If you were to start sampling the cystic fibrosis allele from one generation to the next, what should happen to its frequency over th.
Q5-1- Which of the following is FALSE- If a genetic disease reduces fe.docx
1. Q5.1. Which of the following is FALSE? 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 disease persists in wetter, mosquito-prone regions in Africa. In regions where malaria does
not occur, individuals who are heterozy gous 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 $ 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.
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 allele does not offer any fitness advantage and the population
is small. The allele does not offer any fitness advantage and the population is large. The allele
offers a selective advantage and the population is small. The allele was introduced at a very low
frequency and the population is large. Q5.4. If the frequency of the HbS allele is 0.2 in a
population, what is the frequency of the H b A allele (assuming this is a two-allele system)?
Q5.5. Which of the following would be sufficient for the Hardy-Weinberg equation to accurately
predict genotype frequencies from allele frequencies? p + q = 1 The population is not evolving
due to natural selection. The population is not evolving due to any of the conditions that distupt
Hardy-Weinberg equilibrium. The population is infinitely large. Q5.6. In a population, if the
proportion of individuals who have sickle-cell disease is 0.40 , and the population is assumed to
be at Hardy-Weinberg equilibrium, what is the expected frequency of the HbS allele? (Hint:
What is the genotype of people with sickle-cell disease, and how is that genotype represented in
the Hardy-Weinberg equation?) Use the following additional passage to answer the next
question. Suppose you travel to the future, to a time when neither cystic fibrosis nor tuberculosis
have caused any deaths for many generations. In all of these future populations, the cystic
fibrosis allele still exists at a low frequency. Q5.10. You visit a huge city with millions of people.
If you were to start sampling the cystic fibrosis allele from one generation to the next, what
should happen to its frequency over the next few generations, and why? The allele frequency
should change a lot from one generation to the next due to random genetic The allele frequency
should not change much from one generatiop to the next because the population is large. The
allele frequency should steadily increase due to natural selection. The allele frequency should
steadily decrease due to natural selection. Q5.7. In a population where the proportion of
individuals who are susceptible to malaria (genotype H b A / H b A ) is 0.53 , and the population
is assumed to be at Hardy-Weinberg equilibrium, what proportion of the population should be
heterozygous H b A / H b S ? Use the following passage to answer the next three questions. It
has been hypothesized that people who are heterozygous for the -allele that catises the deadly
genetic condition cystic fibrosis (which, among other symptoms, reduces fertility) are more
resistant to the deadly disease tuberculosis. Q5.8. If the cystic fibrosis allele protects against
tuberculosis the same way the sickle-cell allele protects against malaria, then which of the
following should be ir ire of a comparison between regions with and without tuberculosis? Cystic
fibrosis deaths should be more common in regions with tuberculosis. Cystic fibrosis deaths
2. should be less common in regions with tuberculosis. Cystic fibrosis deaths should be equally
common in both types of regions. Regional differences in the cystic fibrosis death rate should be
purely random and unpredictable. Q5.9. A person who is heterozygous for the cystic fibrosis
allele moves to a small, isolated community where no one previously carried the allele. If the
cystic fibrosis allele protects against tuberculosis the same way the sickle-cell allele protects
against malaria, what should happen to the frequency of the cystic fibrosis allele in the
community over time, and why? The cystic fibrosis allele should disappear from the population,
because a single individual with the allele is not enough for it to proliferate. The cystic fibrosis
allele should increase to a relatively high frequency, because heterozygotes with the allele will
be more likely to survive than others. The cystic fibrosis allele should become fixed in the
population, due to genetic drift. The cystic fibrosis allele should either disappear or increase in
frequency, depending on chance as well as on tuberculosis prevalence and death rate.
