8.2.2 Abnormal Methylation

• In normal cells, methylation occurs predominantly at regions called CpG
• Methylation reduces accessibility for transcription
• Match the key aspect of normal methylation patterns with its description:

  Methylation Site ↔️ CpG islands

  Primary Role ↔️ Gene silencing and regulation
• The addition of methyl groups reduces the ability of transcription factors to bind to DNA.


  True
• Hypomethylation in repetitive sequences can lead to genomic instability
• Match the type of aberrant methylation with its impact on gene expression:

  Hypermethylation ↔️ Silences genes

  Hypomethylation ↔️ Activates genes
• Methylated CpG islands prevent the binding of transcription
• Reduced methylation in repetitive sequences can lead to genomic instability
• What is the primary effect of hypermethylation on gene expression?

  Gene silencing
• Hypermethylation leads to gene activation, whereas hypomethylation results in gene silencing.

  False
• The main role of methylation is to silence or regulate gene expression
• Arrange the key aspects of normal methylation in order of their significance:

  1️⃣ Methylation site: CpG islands

  2️⃣ Base pairs: Cytosine-Guanine rich regions

  3️⃣ Primary role: Gene silencing

  4️⃣ Mechanism: Alters DNA structure
• Methylation occurs at CpG islands, which are regions rich in cytosine-guanine base pairs
• How does DNA methylation affect DNA structure to reduce gene expression?

  Makes DNA more compact
• What is the effect of hypomethylation on genomic stability?

  Genomic instability
• Hypermethylation involves the excessive methylation of CpG islands within or near gene promoter regions.


  True
• Hypermethylation can silence tumor suppressor genes, promoting cancer development.


  True
• Genomic instability can result from reduced methylation in repetitive sequences.


  True
• Aberrant methylation can disrupt normal gene expression and contribute to cancer development.


  True
• Arrange the steps in the process of gene silencing due to hypermethylation:

  1️⃣ Excessive methylation of CpG islands

  2️⃣ Increased DNA compaction

  3️⃣ Blockage of transcription factor binding

  4️⃣ Gene silencing
• Gene silencing by hypermethylation can promote cancer development.


  True
• Hypomethylation typically occurs in gene bodies or repetitive sequences
• Where does hypermethylation primarily occur?

  CpG islands near gene promoters
• How do aberrant methylation patterns contribute to cancer development?

  Disrupt normal gene expression
• What are the two main consequences of hypomethylation in cancer?

  Gene activation and genomic instability
• The primary role of methylation is to silence or regulate gene expression.


  True
• Methylated regions can directly prevent transcription factors from binding to DNA.


  True
• What type of base is typically methylated in DNA?

  Cytosine
• Match the mechanism of DNA methylation with its effect on gene expression:

  Altering DNA structure ↔️ Reduces transcription factor accessibility

  Blocking transcription factor binding ↔️ Prevents gene expression
• What are the two key mechanisms of aberrant methylation?

  Hypermethylation and hypomethylation
• What is the impact of hypermethylation on tumor suppressor genes?

  Silences tumor suppressor genes
• Hypermethylation can silence tumor suppressor genes.


  True
• Match the type of aberrant methylation with its mechanism:

  Hypermethylation ↔️ Excessive methylation of CpG islands

  Hypomethylation ↔️ Reduced methylation in gene bodies
• Hypermethylation can silence tumor suppressor genes, promoting cancer
• Match the feature with the correct type of methylation:

  Hypermethylation ↔️ Excessive methylation of CpG islands

  Hypomethylation ↔️ Reduced methylation in gene bodies
• Methylation in normal cells occurs predominantly at CpG islands.


  True
• Methylation always prevents transcription factors from binding to DNA.


  True
• What is the specific base in DNA that is typically methylated?

  Cytosine
• Match the concept with its effect on gene expression:

  Normal methylation ↔️ Ensures proper gene expression

  Aberrant methylation ↔️ Contributes to cancer development
• Reduced methylation in repetitive sequences can lead to genomic instability