Clue 1: Orient yourself
What stays the same in both performances?
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 stays the same in both performances?
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 same DNA can produce different outcomes because gene activity and developmental context can differ.
On your WebXam
Using the second-hit model to explain incomplete penetrance
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
The same music score can sound different under different controls
A written score can stay the same while tempo, volume, and timing change the performance. Having the instructions does not mean every instruction is used the same way.
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
Which controls change how the score is used?
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 does a changed performance not mean the notes were rewritten?
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 stays the same in both performances?
- 2Which controls change how the score is used?
- 3Why does a changed performance not mean the notes were rewritten?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: What stays the same in both performances?
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: DNA sequence and gene activity are not identical.
Rule 2: Regulators can change when or how strongly genes act.
Rule 3: Variable outcomes can reflect multiple interacting hits.
Where the analogy stops: Gene regulation is a molecular network, not a musical interpretation.
Carry the previous idea forward
An environmental factor changes risk only when evidence links dose, timing, and mechanism, and risk is not destiny.
Today's technical takeaway
The same DNA can produce different outcomes because gene activity and developmental context can differ.
Now map the same rules onto biology
Separate DNA sequence from epigenetic regulation
Written score
DNA sequence
Volume marks
DNA methylation and chromatin regulation
Conductor timing
MicroRNA and other post-transcriptional control
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
DEV17-E1
DNA methylation can change gene activity without changing the DNA letters.
Why it matters: Sequence and regulation are separate layers.
DEV17-E2
MicroRNAs can reduce how much protein is made from target messages.
Why it matters: Post-transcriptional regulation can alter pathway output.
DEV17-E3
Cleft penetrance can vary among people with similar genetic susceptibility.
Why it matters: A susceptibility variant does not force one outcome.
Make the clinical decision
You are comparing two siblings in a research model.
Both carry the same susceptibility variant, but only one has a cleft. Their methylation profiles differ at developmental genes.
APropose regulation as one testable modifier while keeping other factors open.
BClaim the methylation profile proves the only cause.
CClaim identical variants must always produce identical anatomy.
Choose the testable explanation and cite sequence-versus-regulation evidence.
Evidence required
DEV17-E1 + DEV17-E2 Claim ceiling
You may propose an epigenetic modifier. You may not convert an association into a single proven cause.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 17: Same DNA, Different Outcome
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 teratogen is an environmental agent that can disturb normal development, but only if it acts during the structure's critical window.
- Low maternal is studied as a modifiable ; the protective size for clefts is debated and weaker than for neural-tube defects.
If not, review
Today's new idea is only
Epigenetic marks and tiny RNAs change gene activity without changing the , so a on top of a can tip one into clefting while another stays fused.
Goal: Describe how and microRNAs change gene activity without changing the , and use the idea to explain why two embryos with the same can differ.
Know by the end
- 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.
- MicroRNAs (such as miR-140) repress target genes after they are read to fine-tune networks.
- The model explains penetrance: a is the first hit, and an epigenetic or environmental change can be a second hit that tips a into clefting.
1
Two epigenetic tools
Model start: is the study of changes in gene activity that do NOT change the itself.
- adds a methyl group (CH3) to DNA, usually turning a gene ____ (down/off); from Lesson 16 supplies those methyl groups, so nutrition feeds the epigenome.
- MicroRNAs (miRNAs) are small RNAs that ____ (repress) target genes after they are read; even a small change in miR-140 can shift development.
2
The second hit and penetrance
- An inherited is the first hit; an epigenetic change like CDH1 promoter ____ (methylation) can be a that tips a into clefting.
- This explains ____ (penetrance), the fraction of people with a risk who actually show the trait.
- Isolated clefting looks like a ____ (multifactorial) trait: several small pushes adding up, not one all-or-nothing gene.
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: Epigenetic marks and tiny RNAs change gene activity without changing the , so a on top of a can tip one into clefting while another stays fused.
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
Build a two-embryos diagram. Both carry the same small risk allele. Embryo 1 stays under the threshold and the palate fuses. Embryo 2 picks up a second hit (for example, low folate plus a methylation change quieting an adhesion gene) and crosses into clefting. Label the first hit, the second hit, and the outcome for each, then write one sentence on why this additive picture fits an isolated cleft better than a single-gene syndrome.
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: Build a two-embryos diagram. Both carry the same small risk allele. Embryo 1 stays under the threshold and the palate fuses. Embryo 2 picks up a second hit (for example, low folate plus a methylation change quieting an adhesion gene) and crosses into clefting. Label the first hit, the second hit, and the outcome for each, then write one sentence on why this additive picture fits an isolated cleft better than a single-gene syndrome.
| 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 "Build a two-embryos diagram. Both carry the same small risk allele. Embryo 1 stays under the threshold and the palate fuses. Embryo 2 picks up a second hit (for example, low folate plus a methylation change quieting an adhesion gene) and crosses into clefting. Label the first hit, the second hit, and the outcome for each, then write one sentence on why this additive picture fits an isolated cleft better than a single-gene syndrome.".
- 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: Epigenetic marks and tiny RNAs let identical DNA give different outcomes, and isolated clefting behaves like an additive, multifactorial trait. But we just reasoned from human DNA, mouse palates, and zebrafish at once. How do scientists actually watch development happen?