Copyright © 2019, Elsevier Inc. All Rights Reserved. 1Chapter 06: Epigenetics and DiseaseMcCance/Huether: Pathophysiology: The Biologic Basis of Disease in Adults and Children, 8th EditionMULTIPLE CHOICE 1. What genetic process is likely responsible for the occurrence of asthma in only one of a pair of identical twins?a. Epigenetic modificationsb. Genomic imprintingc. Transgenerational inheritanced. MethylationANS: AEpigenetic modifications can cause individuals with the same deoxyribonucleic acid (DNA) sequences (such as identical twins) to have different disease profiles. Imprinting means that either the copy of a gene inherited through the sperm or the copy inherited through the egg is inactivated and remains in this inactive state in all of the somatic cells of the individual. The heritable transmission to future generations of epigenetic modifications is called transgenerational inheritance. DNA methylation occurs through the attachment of a methyl group to the carbon-5 position of a cytosine.PTS: 1 DIF: Cognitive Level: Remembering 2. Prader-Willi syndrome causes a chromosomal defect that is what?a. Initiated by postnatal exposure to a virusb. Inherited from the fatherc. Related to maternal alcohol abused. Transferred from mother to childANS: BPrader-Willi syndrome can be caused by a 4 Mb deletion of chromosome 15q when inherited from the father. This disorder is not caused by a virus, or related to maternal alcohol abuse. The same gene deletion causes Angelman syndrome when inherited from the mother.PTS: 1 DIF: Cognitive Level: Remembering 3. What can a malfunction in DNA methylation lead to?a. Hypothyroidismb. Blindnessc. Cancerd. Diabetes mellitusANS: CAberrant methylation can lead to silencing of tumor-suppressor genes in the development of cancer. No research supports a connection between hypothyroidism, blindness, or diabetes mellitus to a malfunctioning of DNA methylation.PTS: 1 DIF: Cognitive Level: Remembering 4. Which statement is true regarding the embryonic development of stem cells?a. They are already differentiated.b. They are referred to as housekeeping genes.c. They already demonstrate DNA sequencing.d. They are said to be totipotent.ANS: DEarly in embryonic development, all cells of the embryo have the potential to become any type of cell in the fetus or adult. These embryonic stem cells are said to be totipotent. They are not yet differentiated. Housekeeping genes are necessary for the function and maintenance of all cells. DNA sequencing is not limited to embryonic stem cells.PTS: 1 DIF: Cognitive Level: Remembering 5. When microRNA (miRNA) are methylated their messenger RNA (mRNA) targets are over-expressed. What would be the resulting effect on existing cancer?a. Cell deathb. Metastasisc. Remissiond. RelapseANS: BWhen miRNA genes are methylated, their mRNA targets are over-expressed, and this over-expression has been associated with aberrant function of tumor-suppression genes. This process does not cause cell death, remission, or relapse.PTS: 1 DIF: Cognitive Level: Remembering 6. What is the difference between DNA sequence mutations and epigenetic modifications?a. DNA sequence mutations can be directly altered.b. Leukemia is a result of only DNA sequence mutation.c. Epigenetic modifications potentially can be reversed.d. No known drug therapies are available for epigenetic modifications.ANS: CUnlike DNA sequence mutations, which cannot be directly altered, epigenetic modifications can be reversed. The remaining options are not true statements regarding the difference between DNA sequence mutations and epigenetic modifications.PTS: 1 DIF: Cognitive Level: RememberingCopyright © 2019, Elsevier Inc. All Rights Reserved. 2 7. Which term refers to the silenced gene of a gene pair?a. Activatedb. Alteredc. Mutatedd. ImprintedANS: DGene silencing, a process during which genes are predictably silenced, depending on which parent transmits them, is known as imprinting; the transcriptionally silenced genes are then said to be imprinted. The remaining options do not accurately identify this process.PTS: 1 DIF: Cognitive Level: Remembering 8. What is most likely the shape of the face of a child diagnosed with Russell-Silver syndrome?a. Roundb. Squarec. Triangulard. ElongatedANS: CGrowth retardation, proportionate short stature, leg-length discrepancy, and a small, triangular-shaped face characterizes Russell-Silver syndrome. The other face shapes are not characteristic of Russell-Silver syndrome.PTS: 1 DIF: Cognitive Level: Remembering 9. What are genes responsible for the maintenance of all cells referred to as?a. Universalb. Managerialc. Housekeepingd. ExecutiveANS: CA small percentage of genes, termed housekeeping genes, are necessary for the function and maintenance of all cells. The remaining options do not accurately refer to these cells.PTS: 1 DIF: Cognitive Level: Remembering 10. What is the belief regarding twins who adopt dramatically different lifestyles?a. They may experience very different aging processes.b. They will retain very similar methylation patterns.c. They will experience identical phenotypes throughout their lifespans.d. They may never demonstrate similar DNA sequences of their somatic cells.ANS: ATwins with significant lifestyle differences (e.g., smoking versus nonsmoking) accumulate large numbers of differences in their methylation patterns. The twins, despite having identical DNA sequences, become more and more different as a result of epigenetic changes, which in turn affect the expression of genes. These results, along with findings generated in animal studies, suggest that changes in epigenetic patterns may be an important part of the aging process. They will not experience identical phenotypes throughout their life spans.PTS: 1 DIF: Cognitive Level: Remembering 11. What do hypomethylation and the resulting effect on oncogenes result in?a. A decrease in the activity of the oncogene, thus suppressing cancer development.b. A deactivation of MLH1 to halt DNA repair.c. An increase in tumor progression from benign to malignant.d. An over-expression of microRNA, resulting in tumorigenesis.ANS: CTumor cells typically exhibit hypomethylation (decreased methylation), which can increase the activity of oncogenes. Hypomethylation increases as tumors progress from benign neoplasms to malignancy. Hypomethylation does not result in suppressed cancer development, deactivation of MLH1, or over-expression of
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