Clue 1: Orient yourself
Why are the routes separated?
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
Why are the routes separated?
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: Face-building cells must travel in organized streams to the right destination before they can build the right structure.
On your WebXam
Linking disrupted neural crest migration to a hypoplastic prominence and a possible cleft
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
Transit lines carry different crews to different stations
A transit map has routes, switches, and stations. Riders who begin together can reach different places when a signal sends them onto different lines.
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 a crew exits at the wrong station?
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 information must a route provide besides direction?
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 are the routes separated?
- 2What happens if a crew exits at the wrong station?
- 3What information must a route provide besides direction?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: Why are the routes separated?
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: Movement is organized, not random.
Rule 2: Destination affects what a cell can build.
Rule 3: Too few arrivals can leave a structure small or missing.
Where the analogy stops: Migrating cells respond to molecular cues rather than reading a transit map.
Carry the previous idea forward
Cranial neural crest cells leave the neural folds as flexible builders that can become several craniofacial tissues.
Today's technical takeaway
Face-building cells must travel in organized streams to the right destination before they can build the right structure.
Now map the same rules onto biology
Trace neural crest streams into facial regions
Transit line
Migratory stream
Station
Frontonasal region or pharyngeal arch
Crew shortage
Hypoplasia after reduced cell arrival
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
DEV04-E1
Cranial neural crest cells migrate in reproducible streams.
Why it matters: Their movement has spatial organization.
DEV04-E2
Different streams enter the frontonasal region and pharyngeal arches.
Why it matters: Route and destination are linked.
DEV04-E3
Reduced neural crest survival or migration can cause facial hypoplasia.
Why it matters: Cell number at the destination affects growth.
Make the clinical decision
You are reviewing a lineage-tracing image from a mouse embryo.
One labeled stream reaches the first pharyngeal arch, while a second group stalls near the neural tube.
APredict reduced tissue contribution in the stalled group's destination.
BPredict no effect because cell position never matters.
CClaim the image proves a specific human diagnosis.
Choose the defensible prediction and cite the route and cell-number evidence.
Evidence required
DEV04-E1 + DEV04-E2 Claim ceiling
You may predict a developmental consequence in the model. You may not diagnose Mateo from one animal image.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 4: How Do the Face-Building Cells Get to the Right Place?
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 cells that build most of the face are cranial , which form at the crest of the neural folds where the folding meets.
- To leave home, undergo by an , switching from a stuck-together sheet cell to a free, crawling cell.
Today's new idea is only
is delivery on a schedule: cells must reach the right place, in the right number, at the right time, or a stays hypoplastic and too small to fuse.
Goal: Describe how cranial migrate in organized streams from the neural folds into the and the pharyngeal arches, and explain why correct is required to fill the facial prominences on schedule.
Know by the end
- After , cranial travel in organized migratory streams, each with a destination, not at random.
- The front of the face is filled by cells that migrate into the and the first pharyngeal arch, which becomes the maxillary and mandibular processes.
- must deliver cells in the right place, right number, and right time so the prominences fill out enough to fuse later.
- When is disrupted, a can end up hypoplastic (under-grown) and too small to fuse with its neighbor.
1
Organized streams, not random
Model start: After , cranial travel in organized migratory streams to specific destinations.
- The front of the face is filled by cells that migrate into the and the first ____ arch.
- That first arch becomes the maxillary and ____ processes.
2
Delivery on a schedule
- The cells must arrive in the right place, in the right number, and at the right ____.
- When is disrupted, a can end up ____ (under-grown).
- An under-grown block may be too small to ____ with its neighbor.
3
An honesty note
- We are NOT claiming Mateo had a defect; we are still building the ____.
- Many clefts involve the lip-closing step itself, not the ____ of cells.
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: is delivery on a schedule: cells must reach the right place, in the right number, at the right time, or a stays hypoplastic and too small to 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 · Cell migration and tissue formation in the developing face
WebXam domain
Molecular and Genetic Technology
Evidence to produce
On a side-view sketch of the early embryo, draw three arrows from the neural folds to the three destinations and label each. Circle the two destinations that supply the upper-lip prominences. Then finish a sentence with a real consequence: if the maxillary-bound stream were short by half, the maxillary process would be ____, which could leave a gap because it cannot ____.
Lab / skill
Principles of Biomedical Science (PBS) · Human Body Systems (HBS)
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.
- Claim: Cranial reach the facial prominences by traveling in organized streams, not at random.
- Evidence: The front streams deliver cells into the ____ process and the first pharyngeal ____, which build the lip-forming blocks.
- Reasoning: Because the prominences only fuse if they fill out enough to meet, the cells must arrive in the right place, number, and time, or a block stays hypoplastic and a gap can remain.
How this is graded (rubric)
For: On a side-view sketch of the early embryo, draw three arrows from the neural folds to the three destinations and label each. Circle the two destinations that supply the upper-lip prominences. Then finish a sentence with a real consequence: if the maxillary-bound stream were short by half, the maxillary process would be ____, which could leave a gap because it cannot ____.
| 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 "On a side-view sketch of the early embryo, draw three arrows from the neural folds to the three destinations and label each. Circle the two destinations that supply the upper-lip prominences. Then finish a sentence with a real consequence: if the maxillary-bound stream were short by half, the maxillary process would be ____, which could leave a gap because it cannot ____.".
- 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 face-building cells ride organized streams into the and the first arch, filling the prominences. But the lip is still open: the blocks have arrived and grown, yet they sit next to one another as separate pieces. So the next question is: how and when do those separate blocks actually close to make a lip? We chase that next time.