• Describe the role epigenetics play in the manifestation of traits.
• Identify how environmental factors impact our genetics.
• Identify examples of how epigenetic marks are passed down generationally.

Students will learn how epigenetic modifications change how DNA is expressed. They will also learn what causes these changes and how changes can cause dysregulation. Finally, students will think critically about the heritability of traits and how our environment changes how traits are manifested.

Teacher Preparation

Print the Build a Histone Activity. The second and third pages of this activity will need to be cut out, so single-sided printing is recommended. Watch this how-to video on constructing a model histone.

Print the Epigenetics Lab Notebook (can be double-sided) and the Epigenetics Jigsaw for each student.

Lesson

Follow the Epigenetics Slideshow.

Slides 1-4
Present the case study. Ask students to answer questions one through three in their lab notebooks.

After students have reflected individually, have them pair up and discuss for a couple of minutes. Then, have students share what they discussed with the class.

Slide 5
Clarify what DNA does and how the central dogma of biology works.

Slide 6
Watch this video and emphasize DNA’s 3D structure to students.

Slide 7
If your students haven’t gone through this material yet, use the DNA Transcription and Translation Practice activity to help students understand the basic process. Ask students to reflect on how our cells are different but have the same DNA.

For more information on stem cells and how cells differentiate, use the Immortal Cells Lesson Plan.

Slide 8
Explain how DNA fits into cells and how much it needs to be condensed. Introduce students to the terms euchromatin and heterochromatin. Be sure to point out both on the slideshow’s diagram.

Slides 9-11
Have students label the diagram in their lab notebooks. Explain how DNA gets increasingly condensed closer to the chromosomes. Then, explain the structure of histones (the names of the subunits aren’t important for the lesson). Point out the charges of histones, their tails and the charge of the DNA strand. Have students label the charges in their lab notebooks.

Slides 12-15
Explain to students that epigenetic changes don’t change the DNA sequence and aren’t permanent.

You can illustrate the concept with this analogy: In a sentence, punctuation in different places can change the meaning of the sentence, but not the letters.

Have students compare and contrast epigenetic changes and genetic changes using the chart in their lab notebooks.

Slide 16
Have students note the different examples of modifications made to the histones. Acetylation generally increases expression by loosening the DNA. Methylation generally decreases expression by tightening the DNA.

Explain that there are more possible changes, but these are the most commonly discussed. Have students fill out questions and labels on acetyl and methyl groups in their lab notebooks.

Slide 17
Use the Build a Histone Activity to demonstrate the principles discussed in previous slides. Students will need scissors, tape and paperclips to construct their histone.

Have students cut all the pieces out and help them tape the histones together. They’ll then tape the strands of DNA together. Next, students will wind the DNA strand around the histones.

For instructor guidance, watch this video on how to construct this model.

Have students add or take away methyl and acetyl groups. Then, ask them to demonstrate with the paper model what the addition or removal of each group would do to the DNA.

Slides 18-20
On this slide, note that the names of the proteins aren’t important to the lesson. Explain that many proteins are needed for transcription to happen. If the DNA is too tightly wound on the histone, the proteins can’t fit. Have students demonstrate tightly wound DNA on their histone model. Explain that epigenetics can do more than turn genes off or on. They can also change how much gene product is made.

Slide 21
Ask students to think about what may make epigenetic changes. To prompt them, provide one or two examples from the slide. Give them a minute to write ideas in their lab notebooks, and then present the rest of the slide.

Slides 22-24
Ask students to apply their knowledge to the case study. Discuss what could have caused one twin to get cancer and one to not. Then, go over the scenario and ask the follow-up questions. Have students write their answers in their lab notebooks.

After they have made their hypotheses, explain that Adam will most likely not need to worry about developing cancer. Patrick will most likely not need to worry about having passed an increased risk of cancer to his children. Doctors will advise Patrick to make lifestyle changes (diet, stress management and exercise) along with his cancer treatments.

Slides 25-30
Ask students to think about the last lesson. Then, have them pair up and discuss. Finally, have each pair share their thoughts with the class.

Next, conduct the jigsaw activity. Follow these instructions:

1. Give students an overview of the activity. Emphasize that each student will be responsible for teaching their group members the information in their reading.
2. Split students into three to six groups. Each student in the group will get one of the three reading pages, lettered A through C.
3. Give students five minutes to review their reading and complete the relevant questions in their lab notebooks.
4. Move students into expert groups. These are the students who share the same letter reading page. Allow students five minutes to discuss the questions and answers with their group.
5. Move students back to their original group. Give them eight minutes to teach each other their reading. During this time, each student has two minutes to discuss their reading. Create a rule for who should talk first, such as the student who has the next birthday.
6. As a class, go over some of the main takeaways from the reading pages.

Slide 31-35
Present the conclusion slides.

Discussion

Throughout the lesson, emphasize the 3D structure of DNA, as well as the fact that our epigenetics change a lot.

Focus on all the unanswered questions scientists have about epigenetics. Emphasize that students could be involved in answering them.

Sanford Connection

Jianning Tao, PhD, and his lab currently focus on the mechanisms that affect how osteoblasts (the cells that form new bones) function. The lab’s goal is to guide future treatments of skeletal diseases. Dr. Haydee Torres joined the Tao lab in 2018 and her research has focused on Notch nuclear complexes and their role in the initiation and progression of osteosarcoma. Learn more about the work being done by  Dr. Torres and Dr. Tao.

Answers to Questions in Lab Notebook

Acetyl groups generally (tighten/loosen) DNA, which (increases/decreases) expression.

Methyl groups generally (tighten/loosen) DNA which (increases/decreases) expression.