Epigenetics

• What does gene expression refer to?

  When DNA is expressed to create a protein
• What processes are included in gene expression?

  Transcription and translation
• How is gene expression controlled in eukaryotic organisms?

  Through epigenetics
• What does epigenetics involve?

  A heritable change in gene function
• How does epigenetics affect gene expression?

  By initiating or preventing transcription
• What is the definition of epigenetics?

  Heritable change in gene function without DNA sequence change
• What causes changes in gene function in epigenetics?

  Environmental factors
• What are chemical tags in epigenetics?

  Chemicals that modify DNA or histones
• What is the epigenome?

  The layer of chemical tags around DNA
• How does the epigenome affect DNA structure?

  It affects DNA coiling and accessibility
• What is heterochromatin?

  Tightly coiled DNA
• What is chromatin?

  Loosely coiled DNA
• What is the effect of increased methylation on DNA?

  Inhibits transcription
• Why does increased methylation inhibit transcription?

  It tightly coils DNA, preventing factor binding
• What do acetyl groups do in epigenetics?

  Bind to histones and loosen DNA
• How do acetyl groups affect DNA coiling?

  They repel DNA, making it loosely packed
• What is the relationship between heterochromatin and transcription?

  Heterochromatin inhibits transcription
• What is the role of tumor suppressor genes?

  They slow down cell division
• What happens if there is a mutation in a tumor suppressor gene?

  It results in a non-functioning protein
• Which genes are linked to breast cancer?

  BRCA1 and BRCA2
• How does hypermethylation affect tumor suppressor genes?

  It switches them off by tightly coiling DNA
• What is hypomethylation?

  Insufficient methyl groups added to a gene
• What are oncogenes?

  Genes that trigger mitosis
• What happens if oncogenes are permanently switched on?

  Excessive cell division occurs
• What are the key differences between heterochromatin and euchromatin?

  • Heterochromatin:
  • Tightly coiled DNA
  • Transcription inhibited
  • Caused by increased methylation, decreased acetylation
  • Euchromatin:
  • Loosely coiled DNA
  • Transcription occurs
  • Caused by decreased methylation, increased acetylation
• How does epigenetics relate to cancer development?

  • Tumor suppressor genes:
  • Hyper methylation can switch them off
  • Leads to uncontrolled cell division
  • Oncogenes:
  • Hypo methylation can keep them permanently on
  • Causes excessive mitosis