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
• What is the effect of DNA methylation on gene expression when it occurs at CpG islands?

  Suppresses gene expression
• Histone acetylation can loosen chromatin structure and enhance gene transcription.
• Epigenetic modifications are chemical changes to DNA or histone proteins that influence gene expression without altering the underlying DNA sequence
• What chemical change to histones can loosen chromatin structure and promote transcription?

  Acetylation
• Steps of DNA methylation in gene expression regulation

  1️⃣ Methyl group attaches to DNA, typically at CpG islands

  2️⃣ Transcription factor binding is prevented

  3️⃣ Gene expression is suppressed
• What is the primary effect of DNA methylation on gene activity?

  Suppression
• The two main types of epigenetic modifications are DNA methylation and histone modification
• Match the epigenetic modification with its description:

  DNA Methylation ↔️ Addition of a methyl group to DNA

  Histone Modification ↔️ Chemical changes to histone proteins
• What typically happens to gene expression when methyl groups attach to cytosine within CpG islands?

  Suppression
• Epigenetic modifications can be influenced by environmental factors and are heritable.
• Histone acetylation generally increases gene expression by loosening chromatin structure
• What is the effect of histone methylation on gene expression?

  Can increase or decrease
• In Prader-Willi syndrome, the maternal copy of certain genes is silenced through imprinting.

  False
• Match the epigenetic modification with its role in development:

  DNA Methylation ↔️ Genomic imprinting

  Histone Modifications ↔️ Cell differentiation
• What is the effect of hypermethylation of tumor suppressor genes in cancer?

  Silences the genes