Clue 1: Orient yourself
Why was the temporary wall useful at first?
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 happened to the cells in the seam after the two sides joined?
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: True palatal fusion requires removal of the midline epithelial seam so mesenchyme becomes continuous.
On your WebXam
Distinguishing a settled scientific conclusion from a still-debated mechanism
For life
When something appears after you remove a signal, look for the brake that was holding it down.
Principle: Held down, not gone
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
Remove the temporary wall after two rooms connect
Builders may use a temporary wall while two spaces are being formed. Once the permanent edges meet, the temporary material must be removed to create one open space.
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 must disappear for the rooms to become one space?
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
Which observations could distinguish demolition from wall movement?
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 was the temporary wall useful at first?
- 2What must disappear for the rooms to become one space?
- 3Which observations could distinguish demolition from wall movement?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: What happened to the cells in the seam after the two sides joined?
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 temporary boundary can guide joining.
Rule 2: The boundary must be removed for continuity.
Rule 3: Competing cell mechanisms require direct evidence.
Where the analogy stops: Seam cells can die, extrude, or change behavior. They are not bricks.
Carry the previous idea forward
After elevation, the medial edges must recognize, adhere to, and align with one another before fusion can continue.
Today's technical takeaway
True palatal fusion requires removal of the midline epithelial seam so mesenchyme becomes continuous.
Now map the same rules onto biology
Test what happens to midline seam cells
Temporary center wall
Midline epithelial seam
Remove wall material
Apoptosis or cell extrusion
One continuous room
Mesenchymal confluence across the palate
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
DEV09-E1
A midline epithelial seam forms after the shelves adhere.
Why it matters: The seam is a normal temporary stage.
DEV09-E2
Seam cells are removed through processes that include apoptosis and extrusion.
Why it matters: Cell loss helps eliminate the barrier.
DEV09-E3
Lineage labeling tests whether seam cells remain, move, or change identity.
Why it matters: Mechanism requires tracking, not appearance alone.
Make the clinical decision
You are choosing an experiment to test seam removal.
A still image shows no seam at the endpoint, but the team disagrees about what happened to the seam cells.
AUse lineage labeling plus time-resolved cell-death and extrusion markers.
BUse the endpoint image alone to prove one mechanism.
CAssume all seam cells became bone.
Choose the experiment and explain why the endpoint image is not enough.
Evidence required
DEV09-E1 + DEV09-E2 Claim ceiling
You may distinguish supported cell-removal mechanisms. You may not force all seam loss into one mechanism without tracking evidence.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 9: What Happens to the Wall Between the Shelves: Seam Removal, EMT versus Apoptosis
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
- The -facing edge of each elevated shelf is covered by the , and the very outside is capped by the .
- The is a non-stick protective layer whose normal job is to keep embryonic surfaces from sticking.
Today's new idea is only
The is only finished when the seam is removed, and exactly HOW the seam cells leave is a real scientific question that better imaging keeps refining.
Goal: Explain that the seam must be removed for the to become one continuous , and compare the candidate mechanisms (EMT, , cell , and live-) as a genuine, still-evolving scientific question.
Know by the end
- For the to be one , the on the left and right must become continuous, which requires removing the seam between them.
- Scientists agree the seam disappears, but they have proposed different mechanisms for how its cells leave: EMT, , , and live-.
- found little evidence that seam cells convert to (EMT) and pointed toward plus ; recent favors -driven extrusion plus apoptosis.
- This is normal science: the conclusion (the seam goes away) is settled while the cellular mechanism is still being argued.
1
The seam must go
Model start: The last act of is removing the so the left and right become one continuous .
- Scientists agree the seam ____, but they propose different mechanisms for how its cells leave.
- The classic candidates are EMT (cells convert to ), (cells die in an orderly way), and ____ (cells slide away).
2
Better tools, better answers
- Using ____ labeling, researchers found little evidence for large-scale EMT and more support for plus .
- The newest shows seam cells contract, form rosettes, and undergo live-cell ____ (extrusion).
3
Two layers of certainty
- The conclusion (the seam goes away) is ____, while the mechanism is still being argued.
- For Mateo, seam-removal failure stays a possible cause, not something visible on a ____ exam.
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: The is only finished when the seam is removed, and exactly HOW the seam cells leave is a real scientific question that better imaging keeps refining.
Words to unlock first
midline epithelial seam (MES)epithelial-to-mesenchymal transition (EMT)apoptosiscell extrusionlineage labeling
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 · Cells, tissues, and constructing explanations from evidence
WebXam domain
Molecular and Genetic Technology
Evidence to produce
Write the "open questions" box for Mateo's case file: (1) state what is settled (the seam must be removed for one continuous palate), (2) name the competing mechanisms, (3) say which is currently favored and why (better imaging), and (4) note honestly that the question is not fully closed. Add one line that seam-removal failure stays a possible upstream cause, not something visible on newborn exam.
Lab / skill
Principles of Biomedical Science (PBS) · Biomedical Innovations (BI)
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.
- Lan & Jiang 2015, Cellular and Molecular Mechanisms of Palatogenesis (Curr Top Dev Biol)
- Bush & Jiang 2011, Palatogenesis: morphogenetic and molecular mechanisms of secondary palate development (Development)
- Won et al. 2023, Gene Regulatory Networks and Signaling Pathways in Palatogenesis and Cleft Palate (Cells)
- Claim: For the to become one , the ____ must be removed.
- Evidence: Scientists proposed ____, , , and extrusion; found little ____ and recent imaging favors -driven extrusion plus apoptosis.
- Reasoning: This is a good example of science because the conclusion is settled while the ____ is still being refined by better tools, and for Mateo it stays an possibility we cannot confirm from the outside.
How this is graded (rubric)
For: Write the "open questions" box for Mateo's case file: (1) state what is settled (the seam must be removed for one continuous palate), (2) name the competing mechanisms, (3) say which is currently favored and why (better imaging), and (4) note honestly that the question is not fully closed. Add one line that seam-removal failure stays a possible upstream cause, not something visible on newborn exam.
| 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 "Write the "open questions" box for Mateo's case file: (1) state what is settled (the seam must be removed for one continuous palate), (2) name the competing mechanisms, (3) say which is currently favored and why (better imaging), and (4) note honestly that the question is not fully closed. Add one line that seam-removal failure stays a possible upstream cause, not something visible on newborn exam.".
- 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: The seam is removed, by mechanisms scientists are still working out, so the becomes one continuous . But the seam cells clear at exactly the right time and place, and the shelves grew the right amount and stuck only where they should. Something must be telling the tissue when and where to grow, stick, and clear. What is that signal, and where does it come from? We chase that next time.