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amaranthyak153Lv1

28 Sep 2019

We ran a simulation that graphed the popuulation and allele frquencies (A and B alleles) of three populations. For a simulation where there is no genetic drift, mutation or migration affecting the population, there is still a slow, steady change of the frequency of the A allele over time (all three poplations' allele A frquencies seemed to go towards an allele frequency of 0.500).

a) What is the factor causing the linear curves to all go slowly and steadily towards an allele frequency of 0.500?

b) How is it that allele frequencies can still fluctuate in absence of genetic drift, migration and mutation?

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Tod ThielLv2

28 Sep 2019

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Related questions

a) How is it that allele frequencies can still fluctuate in absence of genetic drift, migration and mutation?

b) Describe the impact of migration on the stability of allele frequencies.

c) Describe the impact of mutation on the stability of allele frequencies. Is a higher mutation rate likely to cause the lost of some alleles?

pinkantelope545

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.

indigosnake469

Q49. Which of the following is NOT true?

If a genetic disease reduces fertility and the allele thatcauses the disease offers no other advantage, the allele willlikely eventually disappear, due to natural selection.

Natural selection does not favor individuals who are homozygousfor the sickle-cell allele, because these individuals typically diebefore they are old enough to reproduce.

Individuals who are heterozygous HbA/HbS areprotected from malaria, and this is why sickle-cell diseasepersists in wetter, mosquito-prone regions in Africa.

In regions where malaria does not occur, individuals who areheterozygous HbA/HbS have a fitness advantageover those who are homozygous for the normal hemoglobin allele(HbA).

Q50. AFTER malaria is cured, the frequency of the HbSallele should decrease in regions with lots of mosquitoesbecause:

People will no longer die from sickle-cell disease in theseregions.

Having one copy of the HbS allele will no longer beadvantageous in these regions.

Natural selection will no longer act on the HbS alleleat all in these regions.

All alleles associated with genetic diseases eventuallydisappear.

Q52. If the frequency ofthe HbS allele is 0.4 in a population, what is thefrequency of the HbAallele (assuming this is atwo-allele system)?

Q53. Which of the following would be sufficient for theHardy-Weinberg equation to accurately predict genotype frequenciesfrom 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 thatdisrupt Hardy-Weinberg equilibrium.

The population is infinitely large.

Q54. In a village, if the proportion of individuals who havesickle-cell disease is 0.25, and the population is assumed to be atHardy-Weinberg equilibrium, what is the expected frequency of theHbS allele? (Hint: What is the genotype of people withsickle-cell disease, and how is that genotype represented in theHardy-Weinberg equation?)

0.1250.250.50.75

Q55. In the same village, what proportion of the populationshould be heterozygous HbA/HbS, according to theHardy-Weinberg equation?

Use the following passage to answer the nextthree questions.

It has been hypothesized that people who are heterozygous forthe allele that causes the deadly genetic condition cystic fibrosis(which, among other symptoms, reduces fertility) are more resistantto the deadly disease tuberculosis.

Q56. If the cystic fibrosis allele protects against tuberculosisthe same way the sickle-cell allele protects against malaria, thenwhich of the following should be true of a comparison betweenregions with and without tuberculosis?

Cystic fibrosis deaths should be more common in regions withtuberculosis.

Cystic fibrosis deaths should be less common in regions withtuberculosis.

Cystic fibrosis deaths should be equally common in both types ofregions.

Regional differences in the cystic fibrosis death rate should bepurely random and unpredictable.

Q57. A person who is heterozygous for the cystic fibrosis allelemoves to a small, isolated community where no one previouslycarried the allele. If the cystic fibrosis allele protects againsttuberculosis the same way the sickle-cell allele protects againstmalaria, what should happen to the frequency of the cystic fibrosisallele 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 toproliferate.

The cystic fibrosis allele should increase to a relatively highfrequency, because heterozygotes with the allele will be morelikely to survive than others.

The cystic fibrosis allele should become fixed in thepopulation, due to genetic drift.

The cystic fibrosis allele should either disappear or increasein frequency, depending on chance as well as on tuberculosisprevalence and death rate.

Use the following additional passage to answer the nextquestion.

Suppose you travel to the future, to a time when neithercystic fibrosis nor tuberculosis have caused any deaths for manygenerations. In all of these future populations, thecystic fibrosis allele still exists at a low frequency.

Q58. You visit a huge city with millions of people. If you wereto start sampling the cystic fibrosis allele from one generation tothe next, what should happen to its frequency over the next fewgenerations, and why?

The allele frequency should change a lot from one generation tothe next due to random genetic drift.

The allele frequency should not change much from one generationto the next because the population is large.

The allele frequency should steadily increase due to naturalselection.

The allele frequency should steadily decrease due to naturalselection.