Block 7 Michigan Genetic - Pt 2

14 Questions | Total Attempts: 145

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Block 7 Michigan Genetic - Pt 2

Questions and Answers
  • 1. 
    Sickle cell anemia is:
    • A. 

      An autosomal dominant disease.

    • B. 

      Always caused by the same point mutation in the beta-globin gene.

    • C. 

      Rarely due to the same mutation in unrelated individuals.

    • D. 

      Caused by mutations in either the alpha-globin gene or the beta-globin gene

    • E. 

      An X-linked recessive disease

  • 2. 
    The pedigree below is from a family with cystic fibrosis, an autosomal recessive condition. What is the best estimate that individual I-3 is a carrier of cystic fibrosis?
    • A. 

      1/4

    • B. 

      1/3

    • C. 

      1/2

    • D. 

      2/3

    • E. 

      3/4

  • 3. 
    Which of the following observations is the strongest evidence for an important genetic component in the causation of type-1 diabetes mellitus (IDDM)?
    • A. 

      Pancreatic B-cell autoantibodies are frequently present

    • B. 

      Approximately 10% of affected individuals have an affected sibling.

    • C. 

      Onset of disease is usually in childhood

    • D. 

      The concordance rate in monozygotic twins is approximately 30%.

    • E. 

      The concordance rate in monozygotic twins is five times that in dizygotic twins.

  • 4. 
    The average recurrence risk for a couple that has had a child with cleft lip, a multifactorial birth defect, is approximately 4%. What is the recurrence risk if the couple has two affected children?
    • A. 

      2%

    • B. 

      4%

    • C. 

      10%

    • D. 

      25%

    • E. 

      50%

  • 5. 
    Ankylosing spondylitis is a chronic inflammatory arthritis affecting the spine and sacroiliac joints. 95% of Caucasian patients are positive for the HLA-B27 haplotype; whereas, 7% of all Caucasians are positive. This is evidence for:
    • A. 

      Association of ankylosing spondylitis with the B27 allele of the HLA-B locus.

    • B. 

      Linkage of ankylosing spondylitis to the HLA-B locus.

    • C. 

      Neither.

  • 6. 
    Which karyotype would be MOST frequently seen in liveborn infants (as opposed to spontaneous abortions)?
    • A. 

      47,XX,+21

    • B. 

      47,XX,+3

    • C. 

      69,XXX

    • D. 

      46,XY,-11,+22

    • E. 

      46,YY

  • 7. 
    The family below is segregating a very rare autosomal recessive disease with 100% penetrance. The disease is present and recognizable at birth and does not decrease fitness. Assume no locus heterogeneity. What is the chance that the fetus (IV-1) is affected with this disease?
    • A. 

      1/4

    • B. 

      1/2

    • C. 

      1/9

    • D. 

      2/9

    • E. 

      4/9

  • 8. 
    The G8 RFLP marker is closely linked to the Huntington disease (HD) locus, and it is useful for linkage analysis in HD families. True or False: The base changes responsible for the G8 polymorphism are also responsible for HD
    • A. 

      True

    • B. 

      False

  • 9. 
    Assuming Hardy-Weinberg equilibrium for alleles at the CFTR (cystic fibrosis) locus in the U.S. Caucasian population, and given that the mutant allele frequency, q, is 1/50, what fraction of this population are carriers of a CFTR mutation?
    • A. 

      (49/50)2

    • B. 

      (1/50)2

    • C. 

      1/100

    • D. 

      1/50

    • E. 

      2/50

  • 10. 
    The proband, III-1, has cystic fibrosis (CF). DNA analysis indicates that III-1 is homozygous for a particular CF mutant, but his grandmother (I-2) is homozygous normal. Assume that q=1/50 for this mutant allele, and that the population is in Hardy-Weinberg equilibrium. What is the chance of I-1 being a carrier of CF?
    • A. 

      100%

    • B. 

      50%

    • C. 

      4%

    • D. 

      2%

    • E. 

      0.5%

  • 11. 
    The proband, III-1, has cystic fibrosis (CF). DNA analysis indicates that III-1 is homozygous for a particular CF mutant, but his grandmother (I-2) is homozygous normal. Assume that q=1/50 for this mutant allele, and that the population is in Hardy-Weinberg equilibrium. What is the chance of II-5 being a carrier?
    • A. 

      100%

    • B. 

      50%

    • C. 

      4%

    • D. 

      2%

    • E. 

      0.5%

  • 12. 
    The proband, III-1, has cystic fibrosis (CF). DNA analysis indicates that III-1 is homozygous for a particular CF mutant, but his grandmother (I-2) is homozygous normal. Assume that q=1/50 for this mutant allele, and that the population is in Hardy-Weinberg equilibrium. What is the chance of III-2 being affected with CF
    • A. 

      100%

    • B. 

      50%

    • C. 

      4%

    • D. 

      2%

    • E. 

      0.5%

  • 13. 
    Prader-Willi syndrome (PWS) can result from either an interstitial deletion involving the paternal copy of chromosome subregion 15q1-q13 or from maternal uniparental disomy of chromosome 15. The reason for this is:
    • A. 

      The maternal copy of the gene(s) responsible for Angelman syndrome (AS) is imprinted and is not expressed.

    • B. 

      PWS results from an anomaly of X-chromosome inactivation

    • C. 

      The paternal copy of the gene(s) responsible for PWS is imprinted and is not expressed.

    • D. 

      The maternal copy of the gene(s) responsible for PWS is imprinted and is not expressed

    • E. 

      The maternal copy of the gene(s) responsible for PWS exerts a dominant negative effect of the paternal allele

  • 14. 
     Familial retinoblastoma (FRB) is an autosomal dominant cancer predisposition syndrome, due to a defect in the RB tumor suppressor gene. An affected individual typically inherits a single defective copy from one parent, and a normal copy from the other parent. Below are Southern blots for an individual with FRB; both normal and tumor cells were typed for three RFLP markers flanking the RB locus on chromosome 13 (N = normal cells, T = tumor cells). Based upon these data, which of the following is the most likely explanation for the loss of heterozygosity in this individual?
    • A. 

      Mitotic crossover

    • B. 

      Loss of the normal chromosome 13

    • C. 

      Independent second mutation

    • D. 

      Loss of the normal chromosome 13 and reduplication of the mutant chromosome 13

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