Mitosis and Cellular Differentiation Model (HS-LS1-4)
Teacher Notes
Estimated Time: 45 - 60 minutes Materials: Internet-connected device, simulation (Mitosis and Cellular Differentiation Model)
NGSS Alignment (HS-LS1-4):
- SEP: Developing and Using Models. Students interact with the simulation model to identify how cell division produces genetically identical cells, while differentiation creates specialized tissues.
- DCI: LS1.B: Growth and Development of Organisms. Students gather evidence that multicellular organisms begin as a single cell, which divides via mitosis.
- CCC: Systems and System Models. Students use the model to observe inputs/outputs and how the cellular level interacts to form the organism level.
Evidence Statements Addressed:
- 1.a.i, 1.a.ii, 1.a.iii (Components of the model): Students identify genetic material variants, parent/daughter cells, and the multicellular organism.
- 2.a.i, 2.a.ii (Relationships): Students explicitly observe that mitotic division produces two genetically identical daughter cells from a parent cell.
- 2.a.iii: Students observe differentiation into specialized tissues due to gene expression rather than changing genetic material.
- 3.a.i, 3.a.ii, 3.a.iii (Connections): Students observe mitosis allowing growth, differentiation into cell types, and maintaining a complex organism.
Part 1: Engage (Anchoring Phenomenon)
You began your life as a single fertilized egg cell (zygote). Today, your body is made up of over 30 trillion cells, including specialized cells like muscle cells that help you move, nerve cells that transmit signals, and skin cells that protect you. Yet, almost every single one of those 30 trillion cells contains the exact same genetic instructions (DNA).
Question: How can a single cell turn into an entire organism with many different types of specialized cells if they all have identical DNA?
Your Initial Ideas: __________________________________ __________________________________
Part 2: Explore (Simulation Investigation)
Investigation A: The Organism Level (Development)
- Open the Mitosis and Cellular Differentiation Model.
- Ensure you are on the Organism Level view (click the blue button at the top).
- Under the “Development Stage” panel, start at 1. Zygote. Record the starting stats in the table below.
- Click the “Advance Development” button step-by-step through each stage. Watch the main animation panel and record the data in the table for each stage.
Data Table 1: Organism Development
| Stage Name | Total Cells | Process | Genetic Info |
|---|---|---|---|
| 1. Zygote | ____ | ____ | ____ |
| 2. Cleavage | ____ | ____ | ____ |
| 3. Blastula | ____ | ____ | ____ |
| 4. Gastrulation | ____ | ____ | ____ |
| 5. Specialized Tissues | ____ | ____ | ____ |
Investigation B: The Cellular Level (Mitosis)
- Switch to the Cellular Level view using the top toggle button.
- Ensure the “Chemical Treatment” dropdown is set to None (Normal Mitosis).
- Drag the Time (Cell Cycle Progress) slider to watch a single parent cell divide.
- Carefully read the text output below the slider as the cell progresses from 0% to 100%.
Data Table 2: Normal Mitosis Observation
| Phase (Slider %) | What happens to the DNA/Chromosomes? | What happens to the cell structure? |
|---|---|---|
| 0% (Start) | _______________ | _______________ |
| ~30% | _______________ | _______________ |
| ~75% | _______________ | _______________ |
| 100% (End) | _______________ | _______________ |
- Now, change the “Chemical Treatment” to Colchicine (Spindle Inhibitor). Move the slider to 100%.
- Observation: _________________________
- Next, change the “Chemical Treatment” to Hydroxyurea (DNA Synth Inhibitor). Move the slider to 100%.
- Observation: _________________________
Part 3: Explain (Sensemaking)
1. Based on your observations in Investigation A, describe what happens to the genetic information of the cells as the organism grows from 1 cell to a massive number of cells. __________________________________ __________________________________
2. Based on your observations in Investigation B, what is the specific role of mitosis in this process? What are the “inputs” and “outputs” of a single mitotic division? __________________________________ __________________________________
3. In Investigation A, at the “Gastrulation” and “Specialized Tissues” stages, the cells began to change their appearance and function (differentiation). Did their genetic information change during this time? If the DNA is the same, how do you think the cells become different? (Hint: Think about reading a massive instruction manual—do you have to read every single page for every job?) __________________________________ __________________________________
Part 4: Elaborate / Evaluate (Argumentation)
Student Deliverable: Using evidence gathered from the simulation model, write a short scientific explanation that illustrates how a single fertilized egg can develop into a complex, maintained organism.
Your explanation must include the following components:
- How mitosis allows the organism to grow by producing genetically identical daughter cells.
- How differentiation allows those identical cells to form complex, specialized tissues (like skin, muscle, or nerve cells) based on gene expression rather than changing the genetic material itself.
- How mitosis is also used to maintain the complex organism (e.g., replacing dead or damaged cells).
Your Scientific Explanation: __________________________________ __________________________________ __________________________________ __________________________________ __________________________________ __________________________________
Extension (Optional)
In Investigation B, you tested chemical treatments like Colchicine and Hydroxyurea. These chemicals are sometimes used as chemotherapy drugs to treat cancer. Based on your observations of what these chemicals do to the cell division process, explain why they might be effective treatments for a disease that is characterized by uncontrolled, rapid cell division.