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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 – 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 parent’s genotypes to predict her risk of being a carrier of cystic fibrosis. You should be able to determine her parent’s 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 Fiancé Robert take the test as well. Lei’s 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 Robert’s risk of having a child with CF? Male/ Female b. Write down your explanation to Lei and her Fiancé: 3. Another patient, Mark, comes to you because his father has just been diagnosed with the rare genetic disorder known as Huntington’s disease. Mark would like to know his potential risk of developing the disease (you must read about the inheritance pattern of Huntington’s disease in the Lecture and online games to answer this correctly!). Assume that his mother is showing no signs of Huntington’s disease. a. Fill in the Punnett Square below to predict Mark’s risk of getting Huntington’s disease. Male/ Female b. Your explanation to Mark:

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30 Jul 2019

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Related questions

Cystic Fibrosis (CF) is an autosomal recessive genetic disease that is characterized by the secretion of thick, abnormal mucous in the lungs. The mutated gene that leads these symptoms is the CF transmembrane conductance regulator (CFTR gene). The encoded protein is a chloride channel that moves chloride ions out of epithelial cells. In a homozygous individual, the lack of this chloride channel function in a mutant slows the flow of water into extracellular spaces. This lack of water export leads to the heavy mucus in the lungs of CF patients. Although children with CF would die in childhood, current treatments provide life expectancies into the 30’s.

CF is the most frequently inherited genetic disorder among American children. It affects 1 of every 2,500 children; 30,000 currently have the disease. Although its frequency is higher in European populations, it affects all human populations. Heterozygous carrier frequencies in the US are estimated to be 1 out of 29 Caucasians, 1 out of 46 Hispanics, 1 out of 61 African Americans and 1 out of 90 Asians. There are genetic screens for carriers of CF but they are not routinely performed despite this high frequency of carriers. At least all states in the US proscribe testing of newborns to identify children with CF early so that treatment can be started. Newborn tests for CF: http://www.cff.org/AboutCF/Testing/NewbornScreening/ScreeningforCF/ . If CF is such a common genetic disease, and such a simple Mendelian trait, why is genetic screening of parents not done more frequently? Is it just economic, a pain to do, or is it more complex such that the results of genetic testing are not just positive or negative?

Answer the following questions:
1. If two parents are heterozygous carriers of CF, show a pedigree with four children showing the incidence of carriers and afflicted children. If each unafflicted child (carrier or not) mates with another person, who has a 1 out of 30 chance of being a carrier of CF, what is the expected incidence CF disease in the third generation (frequency of CF in any one of grandchildren of the original couple)?

2. Pleiotropy of Cystic Fibrosis. Watch the two videos on the left at:

http://www.cftrscience.com/MOD-animation
or, if you can not view these, read the short NIH Genetics Home Reference for Cystic Fibrosis http://ghr.nlm.nih.gov/condition/cystic-fibrosis

Connect the description with one of the following videos, or related ones (there are many) you see:
video (10 minutes) of daily life of a child with Cystic Fibrosis http://www.youtube.com/watch?v=WUsuGKzdDg8
Laura’s (20 year old) video diary of life with CF http://www.youtube.com/watch?v=Pgrf8qJXhpc&feature=related

In your own words, describe the range of CF phenotypes. List the other organs besides lungs that are affected and how does it affects those organs.

3.The DNA sequence of the CFTR gene is 170,000 base pairs in length and encodes the CFTR protein that is 1480 amino acids long. Open the accompanying text file (in Canvas/Files/Discussion folder) “CFTR gene DNA sequence”. You will see an alignment of the NIH human genome sequence of the CFTR gene – called “Reference” rather than “wild-type”- against a gene sequence containing a common mutation in CFTR. Look at the alignment and determine how the DNA sequence differs between them. What is the position number where they differ? How many and what nucleotides do they differ in? A “-“ mark in one sequence in the alignment means that that base sequence is missing the corresponding bases in the other sequence. The sequence is a long one but the differences are in bolded bright red text. Matching sequence is marked with a | linking the two sequences. Look near the sequence AAATATCATC if you use FIND tool in Word.

In another file, you will an alignment of the reference translated into a protein sequence, compared to the mutant allele translated into protein sequence. The differences are again in red whereas the areas where the proteins match are in black. Look at the alignment. How do these two proteins differ? Again, find the position number and describe how they differ at that location. A “-“ mark in the alignment means that amino acid is missing when compared to the other sequence.

4. Given that the CFTR gene can be analyzed for a mutation that causes CF, couples interested in being tested as carriers face several choices given the results.
What could be a consequence of a false positive result (couple is identified as carriers but they would not produce any children with symptoms)?

What could be a consequence of a false negative result (a test indicates the couple is not both carriers but they would produce some children with CF)?

5. The sensitivity of the test can vary with ethnic group. The following is a chart from the NCBI Genetic testing site. A sensitivity less than 100% would be likely to produce false negative results from an inability to determine that someone is carrier.

CF Carrier Test Sensitivity by Ethnic Group
http://www.ncbi.nlm.nih.gov/projects/GeneTests/static/concepts/primer/ptscarr5.shtml

Ethnic Group 1

Population Frequency of CF

Sensitivity of Carrier Detection 2

Caucasian

1 in 29

90%

Ashkenazi Jewish

1 in 29

97%

Native American

1 in 32

94%

Latino

1 in 46

57%

African-American

1 in 60

75%

Asian

1 in 90

30%

Why might different ethnic populations differ in the ability of the genetic test to identify carriers of CF?

Medical History:
Mrs. KY is a 45 yr old Caucasian female, married with two teenage sons. She is employed as a senior manager at a large bank and reports experiencing an “above average” level of tension and stress. She presents at the referral of her primary care physician, who has observed that the client has elevated blood pressure and cholesterol levels that may be attributed to her stressful and highly sedentary job. In addition, the client admits that she would like to lose 30 to 40 lb (14 to 18 kg) and improve her fitness so that she can ride her bike with her husband on a community rail trail recently installed by her neighborhood.

Diagnosis:
Mrs. KY is a sedentary but otherwise healthy middle-aged female with significant risk factors for cardiovascular disease including obesity, dyslipidemia, and psychosocial stress. At the request of her physician she seeks to start exercising as part of a disease prevention program.

Exercise Test Results:
The client is 5 feet 6 in. tall (168 cm) and weighs 196 lb (89 kg), with a body mass index of 31.7. She has a resting heart rate of 85 beats · min–1 and a resting blood pressure of 136/89 mmHg. Her total cholesterol is 198 mg · dl–1 untreated, and her high-density lipoproteins are 34 mg · dl–1. Her graded treadmill stress test revealed that she has a V.O2max of 20.5 ml · kg–1 · min–1, which is normal for an unfit woman of her age range. Her electrocardiogram was also unremarkable at rest, as well as during and following her test. In addition, she reported smoking from ages 17 to 40. She also complains of occasional joint stiffness in her hands and ankles. The client describes herself as nonathletic and admits to never participating in an organized sport or exercise setting. She is aware of the benefits of exercise but did not feel an incentive to begin a formal program until her doctor’s recommendation. The client jokes that although her workday is highly organized and structured, the rest of her life is chaotic and that it is due only to the support of her husband and kids that anything gets done at home. She laments that her eating habits are atrocious and that she is so tired when she gets home from work that she has only enough energy to make dinner before crashing in front of the television. She presents to you to start a workout program that will help achieve her goals.

Exercise Prescription:
The exercise plan including the traditional components—frequency, intensity, duration, and modality (discussed in detail in later chapters)—may be tailored to address specific risk factors. The subject’s medical history, however, clearly indicates that this person had not prioritized exercise participation until she received her doctor’s recommendation. Moreover, she presents with numerous potential barriers to engaging in a physically active lifestyle, as well as behaviors that contribute to her overweight status. The clinician should assist the participant in establishing awareness and developing strategies to address those barriers. Furthermore, the clinician should consider tailoring strategies for motivating the participant toward the adoption of a healthy, physically active lifestyle.

Questions:
1. Applying the transtheoretical model, at what stage of exercise adoption is this client?

2. Based on your response to question 1, what types of interventions are most appropriate for this stage of change and why?

3. If you used the health belief model, what factors would you emphasize to achieve optimal exercise adherence?

4. How would Bandura’s social cognitive theory be relevant to fostering exercise adherence for this client?

Based on “Morgan: A case of Diabetes” by Lisa Rubin and Clyde Freeman Herreid (National Center for Case Study Teaching in Science)

The Patient:

Morgan Water is a 27-year old Native American that lives on a reservation in Oklahoma. Nearly ¼ of Morgan’s tribe has diabetes but she has no direct family history of diabetes, heart disease, or other serious conditions. She is however obese (BMI = 32) and leads a sedentary lifestyle. Morgan has been suffering from an increasing persistence of symptoms including unusual thirst, dizziness, blurred vision, and numbness in her right foot. The symptoms have been developing over several months but as she is planning her wedding she attributed them to nerves. She is finally persuaded to see her family doctor. Her non-fasting blood glucose level was elevated so the doctor has her return the next morning for a fasting blood sample so they could more accurately measure her blood glucose and insulin. Her blood results are below:

Test

Morgan’s values

Normal range

Pre-Diabetic range

Diabetic range

Plasma glucose, mg/dl

260

70 -139

140 - 199

≥ 200

Fasting glucose, mg/dl

140

≤ 99

100 - 125

≥ 126

A1C, %

7.6

~ 5

5.7 – 6.4

≥ 6.5

Fasting Insulin, mIU/ml

34

2 - 10

10 - 20

≥ 20

Question 1:

Based on her history and blood results, what do you think is the most likely diagnosis for Morgan?

A. Type I Diabetes Mellitus

B. Type II Diabetes Mellitus

C. Pre-Diabetes

D. Cardiovascular Disease

Question 2:

What is the cause of Morgan’s disease?

A. It is an auto-immune disorder that destroys the β-cells of her pancreas so she produces less

insulin than normal.

B. She has a genetic mutation that results in less insulin receptor being produced than normal.

C. She has developed insulin resistance, where her insulin receptors do not recognize the insulin her

body produces, likely due to her obesity.

D. There is no known cause, it can happen spontaneously.

Morgan is worried that she will have to spend the rest of her life giving herself injections but her doctor does not prescribe insulin injections.

Question 3:

Why would injections of insulin not help Morgan if she has hyperglycemia?

A. Her body is already producing excess insulin but not responding to it.

B. Her problem is with her insulin receptors responding to insulin.

C. Excess insulin will only exacerbate her insulin resistance.

D. All of the above.

Question 4:

Given Morgan’s metabolic state, which of the following pathways would you expect to be active in Morgan’s cells (select all that apply)?

A. Glycolysis

B. Gluconeogenesis

C. β-oxidation

D. Amino acid degradation

E. Protein synthesis

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