Clue 1: Orient yourself
Why must the code work only at the handoff point?
Use the labels and the picture's left-to-right, near-to-far, or before-and-after order. Name only what you can point to.
The question
What lets two shelves that already touched finish joining?
Why it matters: The face forms through a timed sequence of growth, movement, and joining. Locating the missed step helps researchers ask a testable question instead of treating every cleft as the same process. Today you practice the professional reasoning behind that work: TGF-beta3 makes the palatal medial edge competent to complete adhesion and seam removal.
On your WebXam
Reading a knockout result to assign a gene to one developmental step
For life
Turn the amount up and down; the result tells you if the signal decides or just allows.
Principle: Boss or doorman?
Five principles we return to
Having it is not using it
Same instructions, different switches
Same look, different cause
Change one thing and watch
Boss or doorman?
Decides the result or only allows it
Held down, not gone
Remove the brake and it returns
Many roads, one ending
One result can begin many ways
Try the everyday version first
A temporary access code enables the final handoff
A temporary code can allow one planned step and then expire. It must be active during the handoff but should not remain after its job is complete.
Do not jump to the biology yet. Treat the picture as a small system. Track its parts, follow one change at a time, and keep more than one explanation open until the picture supplies a way to separate them.
Clue 2: Trace one change
What happens if both teams arrive but the code fails?
Follow one object, stage, or path. Point to the first place where the situation changes instead of jumping to the ending.
Clue 3: Keep the cause open
What result would show that arrival and fusion are separate steps?
List more than one explanation that still fits. Name the extra observation that would help you separate those possibilities.
Now inspect the illustration
Work from the visible evidence. A useful answer names the part of the picture that supports it and leaves unknown causes open.
- 1Why must the code work only at the handoff point?
- 2What happens if both teams arrive but the code fails?
- 3What result would show that arrival and fusion are separate steps?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: What lets two shelves that already touched finish joining?
You can complete today's required check without opening the technical details below.
Ready for the real names? Optional tier 2
Technical rules and limits
Rule 1: A late switch can control a specific transition.
Rule 2: Normal arrival does not guarantee successful joining.
Rule 3: A knockout can separate one step from earlier steps.
Where the analogy stops: TGF-beta3 is part of a molecular network, not a digital password.
Carry the previous idea forward
Signals such as SHH, BMP, and FGF carry local instructions that coordinate growth, position, and cell fate.
Today's technical takeaway
TGF-beta3 makes the palatal medial edge competent to complete adhesion and seam removal.
Now map the same rules onto biology
Read the Tgfb3 knockout result step by step
Teams arrive
Palatal shelves elevate and meet
Access code activates
TGF-beta3 signaling in medial edge epithelium
Final handoff
Stable fusion and seam removal
Educational illustration, not a clinical photograph. Use the labels and evidence cards to make the biological claim.
Mateo's case file: evidence supplied in this lesson
DEV11-E1
In Tgfb3-null mouse embryos, palatal shelves can reach the midline.
Why it matters: Earlier growth and elevation can still occur.
DEV11-E2
The shelves fail to complete normal adhesion and seam removal.
Why it matters: The defect is concentrated at the fusion transition.
DEV11-E3
The result is cleft secondary palate in the model.
Why it matters: Failure of a late step can preserve a gap despite shelf contact.
Make the clinical decision
You are presenting a knockout figure at lab meeting.
Both control and mutant shelves reach the midline, but only controls form continuous mesenchyme.
APlace TGF-beta3 at the fusion and seam-removal step.
BPlace TGF-beta3 only at neural crest birth.
CClaim the mutant shelves never formed.
Choose the step assignment and cite the matched contact evidence.
Evidence required
DEV11-E1 + DEV11-E2 Claim ceiling
You may assign a required role in mouse palatal fusion. You may not claim every human cleft palate is caused by TGFB3.Go deeper Optional tier 3
Everything required for today is above. Open these only if you want the explainer, source trail, or download files.
The everyday model and Tier 1 check are the complete required path for this lesson.
Use these checks to keep your place. They are not turned in through the portal.
Check off as you finish
- Worked through the everyday picture and answered its three questions.
- Completed the Tier 1 check in plain words.
Turn in: Developmental lesson 11: TGF-beta3, the Fusion Switch in the Medial Edge Epithelium
Go to Schoology to turn this in.
Submit one PDF. Put your first and last name in the document header. Name the file: FirstName LastName - Assignment Title - YYYY-MM-DD.pdf.
Open Schoology PDF upload helpIf you cannot get in, see Mr. Mendoza. Do not skip the work.
Optional legacy technical materials Open only if you want the original notes, vocabulary, artifact, and CER work
Before this page, you should know
- A is a chemical message a cell releases to change nearby cells, and the cells that release it are a .
- In the shelf, the and the carry on constant .
Today's new idea is only
does not build the shelves; it licenses the edge cells to stick and dissolve the seam, so without it the shelves grow, elevate, and touch but never fuse.
Goal: Explain that turns on in the medial edge and is required for the shelves to stick and dissolve the seam, and predict the that results when it is missing.
Know by the end
- is a that acts as the switch for the , not a growth or movement gene.
- It turns on only in the , the thin strip of cells that will touch the opposite shelf, by about mouse day E13, right before contact.
- A deletes one gene so we can read its job from what breaks.
- In the the shelves grow, elevate, and touch normally but cannot fuse, so the seam stays and the result is .
1
What TGF-beta3 does
Model start: is a that acts as the switch. It does not build the shelves; the shelves can grow and move without it.
- What it gives the edge cells is , the ability to ____ (stick) to the opposite shelf and then ____ (dissolve) the seam.
- It turns on in the by about mouse day ____ (E13), right before the shelves meet.
2
Reading the knockout
- A removes one gene so we can read its job from what ____ (breaks).
- In the , growth, elevation, and contact are all ____ (normal), but the shelves cannot ____ (fuse).
- , works through Smad2/3 with Smad4 and switches on partner genes including ____ (IRF6) that help break down the seam.
Everything you need for today is on this page. These links are optional.
What to read
Read the short plain-language explanation written for this lesson. Plain-language explainer for this lesson
Why this source matters
This explanation gives you the background for today's idea without making you decode a research paper: does not build the shelves; it licenses the edge cells to stick and dissolve the seam, so without it the shelves grow, elevate, and touch but never fuse.
Words to unlock first
Reading moves
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Stop point
Stop after the final 'Use it now' section. The research citations are available separately for advanced readers.
Your output
Write one claim-evidence sentence: state the main idea, then name the example or evidence that supports it.
Where this fits
Tested on (Ohio WebXam)
Genetics of Disease · 072130
PLTW lesson
MI · Developmental domain · PLTW PBS 072110
WebXam domain
Molecular and Genetic Technology
Evidence to produce
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.
Lab / skill
Principles of Biomedical Science (PBS)
Everything required for today's decision is already in the case file and plain-language explainer. The links below are original papers and database records for teachers and advanced readers, not assigned student reading.
How this is graded (rubric)
For: 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.
| 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. |
How the model answer scores against this rubric
- 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.
What's next: We found the switch that tells edge cells to fuse. But before any cell can be an edge cell, it first had to BECOME a particular kind of cell. How does a face cell decide whether to be bone, skin, or in the first place?