Block 7 Repro Bayes Questions MCQ's

13 Questions | Total Attempts: 267

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Block 7 Repro Bayes Questions MCQ

Questions and Answers
  • 1. 
    II-3 in the family below  has two brothers with hemophllia and three healthy sons. How ikely is it that she is a carrier of the hemophilia gene?
    • A. 

      1in 4

    • B. 

      1 in 2

    • C. 

      1 in 16

    • D. 

      1 in 3

    • E. 

      1 in 9

  • 2. 
    In the family below, two brothers have classical hemophilia, assume that 1-4 (above) has two healthy sons. In that case you can use Bayes' theorem to figure out that her chance of being a carrier is
    • A. 

      10%

    • B. 

      20%

    • C. 

      50%

    • D. 

      12.5%

    • E. 

      33%

  • 3. 
    Your father has a dominantly-inherited form of retinitis pigmentosa, an eye disease that leads to blindness in middle-aged people. Now you are 25 years old, and you took a vision test to check whether you are developing this disease. In two thirds of all people your age who carry the gene, the vision test is abnormal while in one third it is still normal. Your test was normal. How LIKELY is it that you carry the gene?
    • A. 

      1 in 2

    • B. 

      2 in 3

    • C. 

      1 in 16

    • D. 

      1 in 4

    • E. 

      1 in 6

  • 4. 
    Your patient's father died of Huntington's disease. Now the patient is 45 years old and asks you whether he can still get the disease. Two thirds of all patients who carry the Huntington's gene already show signs of the disease by age 45, but your patient is still healthy. Based on this information, how likely is it that he will get the disease?
    • A. 

      1 in 2

    • B. 

      1 in 3

    • C. 

      1 in 9

    • D. 

      1 in 4

    • E. 

      1 in 6

  • 5. 
    The pedigree below segregates for Duchenne muscular dystrophy (DMD), an X-linked recessive condition lethal in males. What is the risk for III-3 of being a carrier for DMD ?
    • A. 

      1 in 2

    • B. 

      1 in 3

    • C. 

      1 in 9

    • D. 

      1 in 10

    • E. 

      1 in 6

  • 6. 
    Retinoblastoma (Rb), a malignant tumor of the eye may be inherited as an autosomal dominant trait. Penetrance is about 4/5 (80%). Michael's paternal grandmother, father and brother had Rb, but Michael is unaffected. What is the risk that Michael's child may develop retinoblastoma?
    • A. 

      1 in 2

    • B. 

      1 in 3

    • C. 

      1 in 9

    • D. 

      1 in 15

    • E. 

      1 in 6

  • 7. 
    Sydney's paternal grandfather died of Huntington disease (HD). Her father is 50 years old and is unaffected. Her brother was diagnosed at 32 years of age with HD. Sydney is now 30 and wants to know her chance to develop HD. (Approximately 10% of HD gene carriers are clinically affected by 30, 50% by age 50, and almost 100% by age 70.)
    • A. 

      3/26

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      1/352

    • E. 

      9/19

    • F. 

      4/22

  • 8. 
    Kim and Peter have two healthy children but Kim's sister has a child recently diagnosed with CF. Peter has no family history of CF. The population carrier frequency is 1/25. What is the chance that Kim and Peter's next child will have CF?
    • A. 

      3/26

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      1/352

    • E. 

      9/19

    • F. 

      4/22

  • 9. 
    Jane is 28 weeks pregnant and consults a genetic counselor because her brother died of severe X-linked hydrocephalus (aqueductal stenosis). She has two unaffected brothers. An ultrasound found that her fetus is a male. Jane already has one unaffected son and one unaffected daughter. What is the chance that Jane's fetus will be affected? (Mother of an isolated case of an X-Inked lethal condition has 2/3 chance of being a carrier (1/3 isolated cases are new mutations).
    • A. 

      1/22

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      1/352

    • E. 

      9/19

    • F. 

      4/22

  • 10. 
    A family is affected with Huntington disease, an adult-onset neurologic disorder. Fifty percent (50%) of people who inherit the HD gene show some symptoms of HD by the age of 50.  Betty is 50 and asymptomatic, but her father died of HD. What is the probability that Betty's son, John, inherited the HD gene?
    • A. 

      1/22

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      1/352

    • E. 

      9/19

    • F. 

      4/22

  • 11. 
    Amanda has a son with Duchenne muscular dystrophy (DMD). There is no other family history of DMD. She has one healthy son and one healthy daughter. She also had a normal CPK level (70% of DMD carriers have a high CPK). What is amanda's daughter's chance to be a DMD carrier?
    • A. 

      1/22

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      3/26

    • E. 

      9/19

    • F. 

      4/22

  • 12. 
    Carol has a son with Duchenne muscular dystrophy. There is no other family history of DMD. The woman's CPK IS normal (70% of obligate DMD carriers have high CPK's). The woman also has two healthy sons. What is the chance that Carol's next child will have DMD?
    • A. 

      1/22

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      1/352

    • E. 

      9/19

    • F. 

      4/22

  • 13. 
    Rebecca has a sister with cystic fibrosis. Her husband, Paul, has no family history of CF. The couple already has one healthy child . What is the chance that their next child could have CF?  
    • A. 

      1/22

    • B. 

      3/92

    • C. 

      1/6

    • D. 

      1/352

    • E. 

      1/199

    • F. 

      4/22

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