Chromatin Structure and Gene Expression

Active learning helps students visualize abstract molecular processes by turning chromatin structure and gene expression into hands-on tasks. These activities make transcription factors, RNAi, and epigenetic changes concrete through modeling, discussion, and peer instruction.

• Year 13
• Biology
• 3 activities
• 20 min–40 min

Learning Objectives

1. Explain the molecular mechanisms by which histone acetylation and deacetylation alter chromatin accessibility and influence gene transcription.
2. Analyze the role of DNA methylation patterns in establishing and maintaining gene silencing, particularly in the context of genomic imprinting.
3. Compare and contrast the structural and functional characteristics of euchromatin and heterochromatin regarding their transcriptional activity.
4. Synthesize information to predict how changes in histone modifications or DNA methylation might affect the expression of a specific gene.
5. Identify specific enzymes responsible for adding or removing acetyl groups from histones and methyl groups from DNA.

Simulation Game

⏱ 30 min·Pairs

Simulation Game: The Transcription Factor Puzzle

Provide students with 'DNA' strips and 'Transcription Factor' shapes. They must find the matching binding sites and demonstrate how the binding of a factor (or the arrival of an oestrogen-receptor complex) allows RNA polymerase to attach and begin transcription.

Prepare & details

Explain how histone acetylation and deacetylation affect chromatin structure and gene expression.

Facilitation Tip: During The Transcription Factor Puzzle, circulate while groups test their models to ask guiding questions about binding specificity and promoter recognition.

Setup: Flexible space for group stations

Materials: Role cards with goals/resources, Game currency or tokens, Round tracker

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Peer Teaching

⏱ 40 min·Pairs

Peer Teaching: The siRNA Silencing Story

In pairs, students create a storyboard explaining the steps of RNA interference. One student explains how double-stranded RNA is cut into siRNA, while the other explains how it guides an enzyme to destroy target mRNA, preventing protein synthesis.

Prepare & details

Analyze the role of DNA methylation in gene silencing and genomic imprinting.

Facilitation Tip: While students prepare The siRNA Silencing Story, remind them to use the RNA interference pathway diagram to sequence events clearly.

Setup: Presentation area at front, or multiple teaching stations

Materials: Topic assignment cards, Lesson planning template, Peer feedback form, Visual aid supplies

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

Think-Pair-Share

⏱ 20 min·Pairs

Think-Pair-Share: Therapeutic Potential of RNAi

Ask students to brainstorm how RNAi could be used to treat a disease like Huntington's or a viral infection. After sharing, the class discusses the challenges of delivering siRNA to specific cells in the human body.

Prepare & details

Compare euchromatin and heterochromatin in terms of their transcriptional activity.

Facilitation Tip: For the Think-Pair-Share on RNAi therapeutics, provide sentence starters to support students who need help framing their arguments.

Setup: Standard classroom seating; students turn to a neighbor

Materials: Discussion prompt (projected or printed), Optional: recording sheet for pairs

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Teaching This Topic

Teachers often start with the misconception that all genes are active in every cell, so begin with a simple model like the lac operon to show regulation. Use analogies carefully, like comparing transcription factors to switches, but clarify that most factors have graded effects rather than on/off states. Research shows that peer teaching and simulations improve understanding of gene silencing pathways like RNAi.

What to Expect

Successful learning looks like students accurately explaining how transcription factors regulate gene expression, tracing the steps of RNAi, and justifying the role of hormones and chromatin states in gene control. They should use precise vocabulary and apply concepts to new examples.

Watch Out for These Misconceptions

Common Misconception

During The Transcription Factor Puzzle, watch for students who assume all transcription factors activate genes.

What to Teach Instead

Use the puzzle pieces to label activators and repressors with different colors and have students explain their choice during the group discussion.

Common Misconception

During The siRNA Silencing Story, watch for students who think RNAi only degrades mRNA and never affects chromatin.

What to Teach Instead

Ask students to include a step in their story where siRNA guides chromatin remodeling complexes to the DNA, using the provided pathway diagram as a reference.

Assessment Ideas

Quick Check

After The Transcription Factor Puzzle, provide a diagram showing a gene locus and ask students to annotate where euchromatin and heterochromatin would form and indicate transcription direction if the gene is active.

Discussion Prompt

During Think-Pair-Share: Therapeutic Potential of RNAi, ask students to discuss how histone acetylation and DNA methylation might interact in a stem cell differentiating into a neuron, using key vocabulary in their responses.

Exit Ticket

After The siRNA Silencing Story, give students a scenario about increased DNA methyltransferase activity and ask them to write two predicted consequences for gene expression using terms like DNA methylation, gene silencing, and heterochromatin.

Extensions & Scaffolding

• Challenge: Have students design a novel siRNA sequence to silence a gene linked to a disease, predicting off-target effects.
• Scaffolding: Provide a partially labeled diagram of the RNAi pathway for students to complete before peer teaching.
• Deeper exploration: Invite students to research how environmental factors like diet affect histone acetylation and connect this to gene expression changes.

Key Vocabulary

Histone acetylation	The addition of an acetyl group to a histone protein, which typically loosens chromatin structure, making DNA more accessible for transcription.
Histone deacetylation	The removal of an acetyl group from a histone protein, which usually results in a more condensed chromatin structure and reduced gene transcription.
DNA methylation	The addition of a methyl group to a DNA base, often cytosine, which is generally associated with gene silencing and can be heritable.
Euchromatin	A less condensed form of chromatin that is generally transcriptionally active, allowing regulatory proteins access to the DNA.
Heterochromatin	A highly condensed form of chromatin that is transcriptionally inactive, with DNA largely inaccessible to transcription machinery.
Genomic imprinting	An epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner, often involving differential DNA methylation.