3.4.2 Epigenetic Modifications

• Epigenetic modifications are chemical changes to DNA or histone proteins that affect gene expression without altering the underlying DNA sequence.
• What is one example of an epigenetic modification that typically suppresses gene expression?

  DNA methylation
• Epigenetic modifications can be influenced by environmental factors and are heritable.
• Match the type of epigenetic modification with its description:

  DNA Methylation ↔️ Addition of a methyl group to DNA

  Histone Modification ↔️ Changes to histone proteins
• In DNA methylation, a methyl group is added to the cytosine base, often in CpG islands.
• Steps involved in histone modification

  1️⃣ Methylation

  2️⃣ Acetylation

  3️⃣ Phosphorylation

  4️⃣ Ubiquitination
• Histone modifications can only decrease gene expression.

  False
• DNA methylation usually suppresses gene expression by preventing transcription factors from binding.
• What happens to chromatin structure during histone acetylation?

  It loosens
• DNA methylation typically occurs at CpG islands, regions rich in cytosine and guanine bases.
• What is the effect of histone acetylation on gene expression?

  Enhances transcription
• DNA methylation typically suppresses gene expression when methyl groups attach to cytosine bases within CpG islands.
• Epigenetic modifications alter the DNA sequence to influence gene expression.

  False
• What is the typical effect of DNA methylation on gene expression?

  Suppression
• Histone acetylation loosens chromatin structure and enhances gene transcription.
• Order the main mechanisms of epigenetic modification based on their typical effect on gene expression.

  1️⃣ DNA methylation: Suppresses gene expression

  2️⃣ Histone acetylation: Enhances gene expression
• Match the epigenetic modification with its typical effect on gene expression:

  DNA Methylation ↔️ Suppression

  Histone Acetylation ↔️ Enhancement
• Where does DNA methylation primarily occur in the genome?

  CpG islands
• Histone modifications include methylation, acetylation, phosphorylation, and ubiquitination.
• Epigenetic modifications can be influenced by environmental factors and are heritable.
• What chemical group is added to DNA during DNA methylation?

  Methyl group
• The two main types of epigenetic modifications are DNA methylation and histone modification.
• What is the impact of DNA methylation on transcription factor binding?

  Prevents binding
• Match the histone modification with its effect on gene expression:

  Acetylation ↔️ Enhances transcription

  Methylation ↔️ Can increase or decrease expression
• Epigenetic modifications alter gene expression without changing the DNA sequence.
• Which region of DNA is typically targeted by DNA methylation?

  CpG islands
• Histone acetylation loosens chromatin to enhance transcription.
• Order the steps involved in DNA methylation's suppression of gene expression.

  1️⃣ Addition of methyl group to DNA

  2️⃣ Methyl group attaches to cytosine

  3️⃣ Transcription factor binding is prevented

  4️⃣ Gene expression is suppressed
• Histone methylation always decreases gene expression.

  False
• What is the primary effect of histone acetylation on gene expression?

  Increases expression
• Epigenetic modifications contribute to phenotypic plasticity and cellular differentiation.
• Hypermethylation of tumor suppressor genes can promote cancer by silencing them.
• Which neurodegenerative disease is associated with changes in histone acetylation?

  Neurodegenerative diseases