Rough draft.This research track is under review with Dr. Atit's lab. Content and sequence may still change.
The Baby Mateo Case
Developmental domainPrinciples of Biomedical Science (PBS)Lesson 18 of 20Your seat: Comparative embryologist
Watching Development Happen
Discovery question
How do we actually watch development go right or wrong?
💡 Because we cannot film a human , scientists use model organisms plus and to watch each step, then reason carefully about what transfers back to a human.
The plan
Prerequisite check
Before this page, you should know
- is the study of changes in gene activity that do not change the itself.
- adds a methyl group that usually silences a gene; a study found 578 methylation positions associated with nonsyndromic CL/P, enriched in regulatory craniofacial regions.
If not, review
Today's new idea is only
Because we cannot film a human , scientists use model organisms plus and to watch each step, then reason carefully about what transfers back to a human.
Learn first
What you will learn
Goal: Explain why scientists use model organisms (mouse, zebrafish) and plus to watch , and judge what each tool can and cannot tell us about a human .
Know by the end
- A is a non-human species studied because it shares key biology and is easier to observe; trust rests on homology, common descent making genes and steps comparable.
- The mouse truly fuses a secondary and its timing maps onto human weeks; the zebrafish is transparent and develops outside the mother but does not make a mammalian secondary palate, so some results need caution.
- permanently tags cells so their descendants can be found later; films development in real time.
- argued against the old cells-migrate-away idea, and revealed seam cells being squeezed out () as the main way the seam disappears.
Learn first
Model: Two ways to watch a fusion (mouse data)
To learn HOW the seam disappears during , scientists combined two techniques in the mouse (PMID:26589921).
(Cre/loxP) permanently tags a group of cells with a color, then looks later to see where their descendants went. When the seam cells were tagged, almost none turned up in the afterward, arguing against the old idea that the cells transform and migrate away.
(time-lapse microscopy of cultured ) films the seam in real time. This revealed seam cells converging, forming rosettes, and being squeezed out of the sheet (live- driven by - cables), with as a partner rather than the only cause. This is a case where better imaging changed the textbook answer.
Do the work
Explore (work the model before reading on)
- Which lets you watch living cells most easily, and why?
- What did rule out, and what did reveal instead?
- Why would a researcher use BOTH and instead of just one?
- Mice and zebrafish are not humans. What feature makes a mouse result trustworthy for a human question, and what makes a zebrafish result need more caution?
- If a new study showed seam cells in a mutant never form rosettes and never get extruded, which earlier step (, seam formation, or seam removal) would you suspect failed, and how would that map onto a ?
The plan
Guided notes
1
Two model organisms
Model start: A is a non-human species studied because it shares key biology with humans and is easier to observe or experiment on.
- The mouse is the workhorse because its truly fuses and its timing maps cleanly onto human weeks, so a mouse mechanism usually ____ (transfers) to humans.
- The zebrafish is transparent and develops outside the mother, so you can ____ (watch) living cells, but it does not make a mammalian secondary , so some results need caution. This rests on ____ (homology).
2
Two seeing tools
- permanently marks cells so you can later find their ____ (descendants).
- films development in real time and revealed ____ () as the main way the seam disappears.
Explore
Reading the Research
What to read
Read the title and the abstract only, not the whole paper. Lan & Jiang 2015, Cellular and Molecular Mechanisms of Palatogenesis (Curr Top Dev Biol)
Why this source matters
This is the published evidence behind today's idea: Because we cannot film a human , scientists use model organisms plus and to watch each step, then reason carefully about what transfers back to a human.
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
You do not need the methods or statistics yet. If a sentence is about lab technique or math you have not learned, mark it and skip it.
Your output
Write one claim-evidence sentence: what this source claims, and the one piece of evidence that backs it up.
Where this fits
Tested on (Ohio WebXam)
Genetics of Disease · 072130
PLTW lesson
MI · Developmental domain · PLTW PBS 072110
WebXam domain
Bio-Molecular Technology
Evidence to produce
You are choosing a model to investigate one open question about Mateo's cleft: "did the medial edge cells fail to get extruded?" Decide whether you would use mouse or zebrafish, name the imaging tool you would pair with it, and write two sentences: one on what the model could show you, and one honest caution about what it could NOT tell you about a human.
Lab / skill
Principles of Biomedical Science (PBS)
Explore
Vetted readings for this lesson
- Lan & Jiang 2015, Cellular and Molecular Mechanisms of Palatogenesis (Curr Top Dev Biol)
- Liu et al. 2016, Irf6 directly regulates Klf17 in zebrafish periderm and Klf4 in murine oral epithelium (journal link; use class excerpt if blocked)
- Schoen et al. 2017, MicroRNAs in Palatogenesis and Cleft Palate (Front Physiol)
The plan
Track your progress today
Check these off as you work through the lesson, then submit. This tells Mr. Mendoza how you're doing so he can help the class. It does not replace turning in your producible.
Use the code Mr. Mendoza gave you, not your name. Saved on this device.
Check off as you finish
- Read the Model and answered the Explore questions.
- Filled in the guided notes in my own words.
- Defined the new vocabulary with an example.
- Built the producible: You are choosing a model to investigate one open question about Mateo's cleft: "did the medial edge cells fail to get extruded?" Decide whether you would use mouse or zebrafish, name the imaging tool you would pair with it, and write two sentences: one on what the model could show you, and one honest caution about what it could NOT tell you about a human.
- Wrote my Claim, Evidence, and Reasoning exit ticket.
Pick your period and code first.
Check yourself
Exit ticket (Claim, Evidence, Reasoning)
- Claim: Scientists (can / cannot) directly watch a mammalian seam disappear.
- Evidence: One plus one imaging tool, and what it showed.
- Reasoning: Why combining models and imaging is more trustworthy than one alone, and what caution applies when moving from animal to human.
How this is graded (rubric)
For: You are choosing a model to investigate one open question about Mateo's cleft: "did the medial edge cells fail to get extruded?" Decide whether you would use mouse or zebrafish, name the imaging tool you would pair with it, and write two sentences: one on what the model could show you, and one honest caution about what it could NOT tell you about a human.
| 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 the right way (Schoology for routine work) 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 "You are choosing a model to investigate one open question about Mateo's cleft: "did the medial edge cells fail to get extruded?" Decide whether you would use mouse or zebrafish, name the imaging tool you would pair with it, and write two sentences: one on what the model could show you, and one honest caution about what it could NOT tell you about a human.".
- 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 turned in on Schoology and confirmed.
Explore
Where this leads: careers
Comparative embryologist Microscopy specialist Research scientist
What's next: Model organisms plus let us watch each step of and pin down which one failed. So a bold question: if we can see exactly which step fails and exactly when, could a scientist step in during the window and prevent a ?