Clue 1: Orient yourself
What determines whether the platforms can meet?
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 determines whether the platforms can meet?
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: The secondary palate begins as paired shelves whose cell growth must create enough tissue to reach the midline.
On your WebXam
Reasoning from a knockout-plus-rescue experiment that signals drive shelf proliferation
For life
Having a gene is not the same as using it.
Principle: Having it is not using it
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
Two stage platforms extend toward the center
Some stages use movable platforms that slide toward a shared center. Both platforms need enough length, room, and timing to meet.
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 would a short platform leave at the center?
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
Why must both sides be measured?
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.
- 1What determines whether the platforms can meet?
- 2What would a short platform leave at the center?
- 3Why must both sides be measured?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: What determines whether the platforms can meet?
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: Growth creates the material needed for contact.
Rule 2: Paired structures must reach a shared target.
Rule 3: A rescue can test whether missing growth caused the gap.
Where the analogy stops: Palatal shelves are living tissues with patterned growth, not mechanical platforms.
Carry the previous idea forward
Upper-lip closure requires growth, contact, and stable fusion at the maxillary-medial nasal boundary.
Today's technical takeaway
The secondary palate begins as paired shelves whose cell growth must create enough tissue to reach the midline.
Now map the same rules onto biology
Connect cell proliferation to palatal shelf length
Extend the platform
Mesenchymal cell proliferation
Reach center stage
Shelf contact at the midline
Restore the extension motor
BMP4 rescue in an Msx1-deficient mouse model
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
DEV06-E1
Secondary palatal shelves grow from the inner sides of the maxillary regions.
Why it matters: The palate begins as paired outgrowths.
DEV06-E2
Reduced mesenchymal proliferation can leave shelves too small to meet.
Why it matters: Cell number and shelf size are connected.
DEV06-E3
Directed Bmp4 expression rescued palatal growth and fusion in an Msx1-deficient mouse model.
Why it matters: The experiment supports a growth mechanism in that model.
Make the clinical decision
You are choosing the readout for a palatal-growth experiment.
Control and mutant embryos are collected before shelf elevation. You can measure only one primary outcome.
AMeasure shelf size and mesenchymal proliferation on both sides.
BMeasure newborn speech before fusion occurs.
CClaim human prevention from the mouse embryos.
Choose the primary outcome and cite the evidence linking cell growth to shelf size.
Evidence required
DEV06-E1 + DEV06-E2 Claim ceiling
You may test a growth mechanism in the model. You may not claim a proven human treatment.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 6: How the Palate Begins: Secondary Palatal Shelf Outgrowth
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 two medial nasal processes merge into the , which becomes the , the four upper incisors, and the primary .
- The upper lip closes at about human weeks 4 to 6 when each fuses with the medial nasal block beside it.
If not, review
Today's new idea is only
A must actively grow to the right size on schedule, driven by signals that tell cells to divide, or the two shelves may never have enough to meet.
Goal: Explain that the secondary begins as two shelves that grow downward from the maxillary processes, and that their growth depends on cell driven by signals in the .
Know by the end
- The roof of the mouth behind the lip is the secondary ; it begins as two palatal shelves that bud from the maxillary processes at about human week 6.
- The shelves first grow vertically (downward), one on each side of the tongue, and are made mostly of neural-crest-derived .
- A shelf reaches full size by (cells dividing), and this growth is driven by signals in the , not automatic.
- If a shelf grows too little, the two shelves may never have enough to meet, and a can result; this is one possibility, not a verdict for Mateo.
1
Where the palate begins
Model start: The roof of the mouth behind the lip is the secondary . It begins as two palatal shelves that bud out from the paired maxillary processes at about human week 6.
- At first the shelves grow ____ (vertically / downward), one on each side of the tongue.
- They are made mostly of ____, the loose inner that came from cranial .
2
Growth is driven, not automatic
- A shelf reaches full size by ____ (), which means cells dividing to make more cells.
- This growth is driven by ____ in the ; remove them and the shelf stays too small and the clefts.
3
Keep it on the table, not as a verdict
- A must grow to the right size on ____.
- For Mateo, a growth failure is one ____ to investigate, not yet something we have ruled in or out.
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: A must actively grow to the right size on schedule, driven by signals that tell cells to divide, or the two shelves may never have enough to meet.
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 · Cell division and growth in secondary-palate formation
WebXam domain
Molecular and Genetic Technology
Evidence to produce
Write the "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.
Lab / skill
Principles of Biomedical Science (PBS) · Medical Interventions (MI)
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)
- Zhang et al. 2002, Rescue of cleft palate in Msx1-deficient mice by transgenic Bmp4 (Development)
- Claim: The secondary begins as ____ that must ____ to reach full size.
- Evidence: In a mouse missing a growth signal, the shelf had ____ and the was ____.
- Reasoning: This matters for Mateo because a could begin as early as the ____ step, before the shelves ever try to meet.
How this is graded (rubric)
For: Write the "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.
| 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 "Act 1: Growth" entry for Mateo's developmental chart in plain language: where the shelves start, which direction they grow, and one reason a shelf might end up too small. Then mark whether there is enough evidence yet to say a growth failure is what happened to Mateo, or whether it is one hypothesis to keep on the table.".
- 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 begins as two shelves that grow downward beside the tongue. But those shelves point straight down, with the tongue sitting between them. How do two downward shelves end up as one flat roof above the tongue? We chase that next time.