Description

1. Which of the following is not true od the trinucleotide repeat expansions that cause the neurodegenerative disorders Huntington disease and the spinocerebellar ataxias?
2. they typically involve large expansions to several hundred or several thousand repeat units.
3. They cosist of CAG repeats located within exons
4. They are considered to be gain of function mutations.
5. Expansion is more likely to occur when the repeat is passed through the father than through the mother
6. In at least some cases, the mutation causes a buildup of protein aggregates in the cell nucleus.

Answer: a

1. Segmental neurofibromatosis, in which disease features are seen in only part of the body, would best be described as
2. inherited mutation
3. new mutation
4. germline mosaicism
5. Somatic mosaicism
6. none of the above

Answer: d

1. Which of the following features is not true of achondroplasia?
2. nearly all disease-causing mutations occur at a single methylated CG dinucleotide within the gene
3. surgical repair is possible for this disorder
4. it is caused by mutations in a fibroblast growth factor receptor gene
5. most cases are the result of a new mutation
6. homozygotes and heterozygotes are equally severely affected

Answer: e

1. Which of the following is true of the Utah population?
2. elevated rates of inbreeding are seen
3. elevated prevalence of PKU, cystic fibrosis, and hemochromatosis
4. relatively high rates of genetic drift
5. genetically similar to northern European populations
6. all of the above

Answer: d

1. In which of the following chromosome abnormalities is mosaicism most likely to be seen?
2. Klinefelter syndrome
3. Down syndrome
4. XXX syndrome
5. Turner syndrome
6. Translocation Down Syndrome

Answer: d

1. Wich of the following best explains variable expression in mitochondrial diseases?
2. locus heterogeneity
3. heterozygosity
4. heteroplasmy
5. modifier loci
6. imprinting

Answer: c

1. Which of the following would be most likely to produce an imbalance in the amount of essential genetic material in the carrier?
2. Robertsonian translocation
3. Paracentric inversion
4. Pericentric inverison
5. Reciprocal translocation
6. Isochromosome

Answer: e

1. Which of the following statements regarding chromosome abnormalities is true?
2. Structural abnormalities increase with paternal age, while abnormalities of chromosome number increase with maternal age
3. All chromosome abnormalities increase wit maternal age
4. For all abnormalities of chromosome number, the extra or missing chromosomes are most often the result of meiotic error in the mother
5. all of the above
6. none of the above

Answer: a,c,d,e

1. Which of the following conditions is most compatible with survival to term?
2. trisomy 13
3. trisomy 18
4. monosomy X (45,X Turner syndrome)
5. monosomy 21
6. trisomy 21

Answer: e

Jorde: Medical Genetics, 4^th Edition

Chapter 7: Biochemical Genetics: Disorders of Metabolism

Multiple Choice

1. It has been suggested that cystic fibrosis (autosomal recessive) has a high prevalence in some populations because heterozygotes are resistant to the effects of chloride-secreting diarrhea. This is best described as an example of
2. Mutation
3. Gene flow
4. Genetic drift
5. Natural selection
6. Linkage disequilibrium

Answer: d

Correct Feedback: d. This is an example of Natural Selection

Incorrect Feedback: a. This is not a mutation

1. This is not an example of gene flow
2. This is not an example of genetic drift
3. This is not an example of Linkage disequilibrium

1. Which of the following is not true of genetic diagnosis using fetal cells in the maternal circulation?
2. PCR is used to amplify DNA from the fetal cell
3. The procedure involves no risk to the fetus
4. The procedure involves virtually no risk to the mother
5. The procedure is more accurate than amniocentesis
6. FISH analysis can be used to detect aneuploidy in the fetal cells

Answer: d

Correct Feedback: Amniocentesis is actually more accurate.

Incorrect Feedback: This is true.

1. Using linkage analysis, you have mapped a disease gene to a 1 magabase (Mb) region of a specific chromosome. Which of the following approaches would be least useful in identifying and cloning the gene?
2. Single strand conformation polymorphisms (SSCP) analysis
3. Testing for cross-species conservation
4. DNA sequencing
5. Isolation of CG islands
6. Radioactive in situ hybridization

Answer: e

Correct Feedback: This would be useful.

Incorrect Feedback: This would be useful.

1. Which of the following is a major difference in the mechanisms for generating diversity in T cell receptors and B cell immunoglobulins (antibodies)?
2. Somatic hypermutation is seen in immunoglobulin genes but not in T cell receptor genes
3. There are multiple variable region genes for immunoglobulins but not for T cell receptors
4. Somatic recombination is seen only in immunoglobulin genes
5. Junctional diversity is generated only in T cell receptor genes
6. Junctional diversity is generated only in immunoglobulin genes

Answer: a

Correct Feedback: This is the major difference.

Incorrect Feedback: This is true for both.

1. Why is there so much MHC (major histocompatibility locus) allelic diversity among individuals in populations?
2. This region is especially susceptible to the effects of genetic drift
3. The MHC region has a high level of somatic hypermutation
4. Diversity enables the population to combat a larger number of different pathogens
5. There are hundreds of different MHC loci, and they are shuffled by somatic recombination
6. MHC diversity ensures that most tissue grafts will be rejected.

Answer: c

Correct Feedback: This is the real reason why ther is so much allelic diversity.

Incorrect Feedback: This is not the reason.

1. A likely explanation for autoimmune disease is
2. Repeated infection by the same microbe eventually stimulates an autoimmune response
3. Depletion of T cell activity as a result of interleukin deficiency
4. Depletion of B cell activity as a result of interleukin deficiency
5. Lack of a memory B cell response
6. Mimicry of self proteins by a foreign pathogen

Answer: e

Correct Feedback: This is the most likely explanation for an autoimmune disease.

Incorrect Feedback: This is not very likely.

1. A Northern Blot is used to
2. Test polymorphisms in linkage analysis
3. Analyze protein variation
4. Analyze DNA sequence
5. Analyze gene expression in different tissues
6. Analyze a Southern blot that has mistakenly been run upside down

Answer: d

Correct Feedback: d. A Northern blot is a gene expression assay in which mRNA on a blot is hybridized with a labeled probe.

Incorrect Feedback: a. This is not a possible use.

1. This requires a Western Blot.
2. This requires a Southern Blot.
3. Southern Blots use DNA and Northern blots use mRNA. Therefore they are not interchangeable.

1. Which of the following is true of autosomal dominant breast cancer?
2. It is characterized by locus heterogeneity
3. It accounts for nearly half of all breast cancer cases in the United States
4. It can be detected by hybridization with a single oligonucleotide probe
5. Penetrance is close to 100%, with nearly all gene carriers developing breast cancer by age 80
6. Autosomal dominant breast cancer affects females but not males

Answer: a

Correct Feedback: This is a characteristic of autosomal dominant breast cancer.

Incorrect Feedback: This is not true.

1. Which of the following is not true of type 2 diabetes (non-insulin dependent diabetes)
2. This form of diabetes is more highly heritable than type 1 diabetes
3. Susceptibility to type 2 diabetes is partially due to the MHC and insulin genes
4. Diet and exercise can decrease susceptibility to this form of diabetes
5. MODY (maturity onset of diabetes in the young) is considered a highly heritable subset of this form
6. This type of diabetes typically has a later age of onset than type 1 diabetes

Answer: b

Correct Feedback: This is not involved in the susceptibility to type 2 diabetes.

Incorrect Feedback: This is true.

1. Huntington disease is thought to be caused by a gain-of-function mutation. Which type of gene therapy would be potentially effective in treating this mutation?
2. Replacement therapy with retroviral vectors
3. Replacement therapy with adenovirus vectors
4. Replacement therapy with adeno-associated vectors
5. Antisense therapy
6. All of the above

Answer: d

Correct Feedback: d. This would be potentially effective.

Incorrect Feedback: a. Replacement therapy is not very effective against gain-of-function mutations.

1. Replacement therapy is not very effective against gain-of-function mutations.
2. Replacement therapy is not very effective against gain-of-function mutations.
3. One of the above is true.

1. A neural tube defect (anencephaly or spina bifida) could be detected by
2. Amniocentesis
3. Chorionic villus sampling
4. Ultrasound
5. A and B
6. A and C

Answer: e

Correct Feedback: e. A and c will detect a neural tube defect.

Incorrect Feedback: a. C is also right.

1. This will not detect a neural tube defect.
2. A is also right.
3. A and c are right, not b.

1. Which of the following is not an indication for prenatal diagnosis by amniocentesis?
2. Previous child with a serious chromosome abnormality
3. Both parents are heterozygous carriers of a mutation that causes Tay-Sachs disease
4. Both parents have bipolar affective disorder (manic depression)
5. Maternal age > 35
6. Previous child or children with a neural tube defect

Answer: c

Correct Feedback: Amniocentesis would not help to detect this.

Incorrect Feedback: Amniocentesis would help in this case.

1. Which of the following would not be involved in a quantitative trait locus analysis?
2. Linkage analysis
3. Breeding of experimental animals
4. Search for human homologs with a non-human probe
5. Estimation of heritability
6. Positional cloning of a disease-causing gene

Answer: d

Correct Feedback: This is not involved.

Incorrect Feedback: This would be involved.

1. Which of the following genetic abnormalities is not associated with Alzheimer disease?
2. Mutations in the beta-amyloid precursor protein (BAPP) gene
3. Presenlilin mutations
4. Trisomy 21
5. Apolipoprotein E e4 allele
6. LDL receptor mutations

Answer: e

Correct Feedback: This is not associated with Alzheimer disease.

Incorrect Feedback: This is associated with Alzheimer disease.

1. Match each phrase with the most appropriate description. Answers can be used more than once.

Age-related macular degeneration

1. BRCA1 and BRCA2 (breast cancer) gene products
2. HOX (homeobox) gene family
3. Leptin mutations
4. Stargardt’s disease mutations
5. Glucokinase mutations

Answer: d

Correct Feedback: d. This is seen with age-related macular degeneration

Incorrect Feedback: a. This is seen in interactions with the Rad51 DNA repair system

1. This is seen in transcription factors involved in limb development
2. This is seen in obesity.
3. This is more common with Maturity onset diabetes of the young (MODY)

1. Match each phrase with the most appropriate description. Answers can be used more than once.

Interact with the Rad51 DNA repair system

1. BRCA1 and BRCA2 (breast cancer) gene products
2. HOX (homeobox) gene family
3. Leptin mutations
4. Stargardt’s disease mutations
5. Glucokinase mutations

Answer: a

Correct Feedback: a. This is seen in interactions with the Rad51 DNA repair system

Incorrect Feedback: b. This is seen in transcription factors involved in limb development

1. This is seen with obesity.
2. This is seen with age-related macular degeneration
3. This is more common with Maturity onset diabetes of the young (MODY)

1. Match each phrase with the most appropriate description. Answers can be used more than once.

Transcription factors involved in limb development

1. BRCA1 and BRCA2 (breast cancer) gene products
2. HOX (homeobox) gene family
3. Leptin mutations
4. Stargardt’s disease mutations
5. Glucokinase mutations

Answer: b

Correct Feedback: b. This is seen in transcription factors involved in limb development

Incorrect Feedback: a. This is seen in interactions with the Rad51 DNA repair system

1. This is seen with obesity.
2. This is seen with age-related macular degeneration
3. This is more common with Maturity onset diabetes of the young (MODY)

1. Match each phrase with the most appropriate description. Answers can be used more than once.

Maturity onset diabetes of the young (MODY)

1. BRCA1 and BRCA2 (breast cancer) gene products
2. HOX (homeobox) gene family
3. Leptin mutations
4. Stargardt’s disease mutations
5. Glucokinase mutations

Answer: e

Correct Feedback: e. This is common with Maturity onset diabetes of the young (MODY)

Incorrect Feedback: a. This is seen in interactions with the Rad51 DNA repair system

1. This is seen in transcription factors involved in limb development
2. This is seen with obesity.
3. This is seen with age-related macular degeneration