Identical Twins, Identical Fates? An Introduction to Epigenetics

M3 Case Study Report Form

Study the case study about epigenetics:
Identical Twins, Identical Fates? An Introduction to Epigenetics

Add your answers to the following questions from the case study and then submit this completed case study report form.

Part I – Coming Home

1. What exactly are twins, and how do they arise? Your response should distinguish between the two different types of twins.

2. Are identical twins completely identical? Why or why not?

3. What can studying twins tell us about the genetic influence on a particular trait?

Part II – The Diagnosis

1. What causes genetic variation? For example, what causes some people to have curly hair and others to not? What causes some people to have a genetic disease such as cystic fi brosis and others to not?

2. What does it mean when a trait or a disease “runs in families”?

3. What could be some possible genetic and non-genetic causes of Shannon’s schizophrenia?

Part III – Just How “Identical” Are We?

1. Briefly describe what you know about the structure of DNA and how DNA is packaged in a cell.

2. At the molecular level, speculate on some ways that the environment might have an influence on DNA and its packaging.

Part IV – What Really is “Epigenetics”?

1. Examine the data shown in Figures 2 and 3. Carefully compare the DNA methylation profiles from the 3-year-old twins versus the 50-year-old twins and summarize your observations. Which set of twins (3-year-old or 50-year-old) have the most similar DNA methylation profiles? Provide a brief explanation of your observations.

2. What types of environmental factors can influence DNA methylation?

3. Aside from DNA methylation, what other types of epigenetic modifications can occur within the genome to influence gene expression?

4. Do you think Elise needs to be worried about her own mental health? Why or why not? If you were a health-care professional, what would you advise Elise to do?

Part V – What Does the Research Say?

You are encouraged to consult reliable sources (such as your textbook and other online and print resources) to answer some of these questions. The NCBI’s Online Mendelian Inheritance in Man (OMIM) is a useful resource for examining the role of reelin in the brain.

1. What is the role of reelin in the brain? According to Figure 5, how does the expression of reelin in the prefrontal cortex of schizophrenic patients differ from reelin expression in non-psychotic subjects?

2. Study the promoter methylation data shown in Figure 6. How does the overall level of methylation of the reelin promoter in schizophrenic brains compare to the methylation of the reelin promoter in non-psychotic control brains? What would be the most probable effect of this methylation pattern on the expression of reelin in patients with schizophrenia?

3. What is the enzyme responsible for methylating DNA? How does a drug like doxorubicin affect DNA methylation?

4. In reference to Figure 7, what is the effect of doxorubicin treatment on the expression of reelin in NT-2 cells? How does increasing amounts of doxorubicin affect reelin expression in these cells?

5. Based on these data, might a drug like doxorubicin be a potential treatment for schizophrenia? Why or why not? What additional experiments should be performed before a drug like doxorubicin goes into clinical trials?