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16 Apr 2018

Homer has a sister with the homozygous recessive disease, cystic fibrosis, caused by the disease allele,
CF â. Homer does not have cystic fibrosis. Neither of their parents have cystic fibrosis. What is the
probability that he does NOT carry the CF â allele (that he is CF+CF+)?

answer is 1/3.

Please WLAK ME THROUGH this problem, thanks

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Jean KeelingLv2

18 Apr 2018

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1) You have been hired as a genetic counselor. Your first patient is a young woman named Lei who comes to you because her brother has cystic fibrosis. (Learn more about this disease in the PowerPoint slides â find out how it is inherited, is it dominant or recessive?) Lei is healthy but would like to know the risk that she is a carrier for the disease. Both her parents are healthy as is her older sister. a. Fill in the Punnett Square below with her parentâs genotypes to predict her risk of being a carrier of cystic fibrosis. You should be able to determine her parentâs genotypes from information given above. Male/ Female b. Explain to Lei her risk of being a carrier: 2). A blood DNA test for the cystic fibrosis allele becomes available and you recommend to Lei that she take the blood test and that her FiancÃ© Robert take the test as well. Leiâs test shows that she is a carrier. Robert is not. What is the risk that their future child will have cystic fibrosis? a. Use the Punnett Square below to predict Lei and Robertâs risk of having a child with CF? Male/ Female b. Write down your explanation to Lei and her FiancÃ©: 3. Another patient, Mark, comes to you because his father has just been diagnosed with the rare genetic disorder known as Huntingtonâs disease. Mark would like to know his potential risk of developing the disease (you must read about the inheritance pattern of Huntingtonâs disease in the Lecture and online games to answer this correctly!). Assume that his mother is showing no signs of Huntingtonâs disease. a. Fill in the Punnett Square below to predict Markâs risk of getting Huntingtonâs disease. Male/ Female b. Your explanation to Mark:

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.

amaranthherring501

Part II: Inheritance of Traits or Genetic Disorders

Background: Cystic fibrosis is an inherited disease that affectsthe respiratory, digestive, or reproductive systems of the body,with symptoms ranging from mild to severe. Bob and Sally arerecently married. Upon deciding to plan a family, both Sally andBob find out that they are both heterozygous for cystic fibrosis,but neither of them has symptoms of the disorder.

Assignment details: Complete a Punnett Square for cystic fibrosisfor this couple using the following alleles: C = normal allele; andc = allele for cystic fibrosis.

Complete the Punnett Square in the graphic organizer.

Also answer the following questions:
Based on the Punnett square, calculate chances (percentages) forthe following:

â¢for having a healthy child (not a carrier)
â¢a child that is a carrier for the cystic fibrosis trait
â¢a child with cystic fibrosis
Be sure to submit these percentages as part of your assignment inthe Graphic Organizer.