TGF-beta3, the Fusion Switch in the Medial Edge Epithelium
Developmental domain · Lesson 11 of 20 · Principles of Biomedical Science (PBS)
Today's goal: Explain that TGF-beta3 turns on in the medial edge epithelium and is required for the shelves to stick and dissolve the seam, and predict the cleft that results when it is missing.
This is a model of the work you should turn in. Use it to check your own: match the structure and the level of detail, do not copy it. Your wording should be your own.
Correction: It is not true that an open palate always means the shelves never grew. In Tgfb3-knockout mice the shelves grew to normal size, elevated, and even touched at the midline, yet the palate still stayed open because the seam never dissolved (PMID:26589921). So growth is only one of several steps, and a separate step, fusion licensed by TGF-beta3 in the medial edge epithelium, can fail on its own and leave a cleft.
This model shows the level of evidence and organization needed to complete: A short evidence-based correction that separates the growth step from the fusion step.
- Write one defensible claim.
- Choose specific evidence that supports the claim.
- Explain the scientific rule that connects the evidence to the claim.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Label on a 4-panel cartoon (grow, elevate, touch, fuse) which single panel the knockout breaks.
The finished product above did not appear all at once. Here is the path from the question to the turned-in work, so you can follow the same steps.
- 1Start from today's question: What lets two shelves that already touched finish joining?
- 2Work the Model and the Explore questions to reason it out before writing anything.
- 3Pull the specific evidence the product needs from the reading and any database you used.
- 4Write it up in the required format: A junior scientist writes: "Mateo's must mean his shelves never grew." Write two sentences correcting this. Name at least one OTHER step besides growth that could fail and still leave an open palate, and cite as your evidence for why growth alone is not the whole story.
- 5Check it against the rubric, then submit.
| Criterion | Proficient | Developing | Beginning |
|---|---|---|---|
| Complete | Every required part of the artifact is present and filled in. | Most parts are present, but one is missing or left blank. | Several parts are missing. |
| Accurate | The science and data are correct and match the evidence. | Mostly correct, with a small factual slip. | Key science or data is wrong. |
| Scientific reasoning (CER) | States a claim, backs it with specific evidence, and explains the reasoning. | Has a claim and evidence, but the reasoning is thin or missing. | Gives an answer with no evidence or reasoning. |
| Professional communication | Clear, organized, and labeled the way a clinician or scientist would write it. | Readable but disorganized or missing labels. | Hard to follow. |
| Submitted | Turned in through the route named under Submit here and confirmed. | Turned in, but in the wrong place or unconfirmed. | Not turned in. |
- CompleteProficient: Nothing is left blank: the model fills every part of "A junior scientist writes: "Mateo's cleft must mean his palate shelves never grew." Write two sentences correcting this. Name at least one OTHER step besides growth that could fail and still leave an open palate, and cite TGF-beta3 as your evidence for why growth alone is not the whole story.".
- AccurateProficient: Every number and claim matches the case evidence.
- Scientific reasoning (CER)Proficient: It names a claim, cites the specific evidence, and explains the reasoning, not just the answer.
- Professional communicationProficient: It is organized and labeled like a real chart note.
- SubmittedProficient: It would be attached to your class form or handed in, and confirmed.
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.
It builds this reusable test skill: Reading a knockout result to assign a gene to one developmental step.
- Name the concept or data pattern being tested.
- Cross out choices that violate that rule or the evidence.
- Justify the best remaining choice before checking the answer.