Clue 1: Orient yourself
Can one small weight tip the scale by itself?
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
Can one small weight tip the scale by itself?
Why it matters: Genetic results can change family counseling and research decisions. They must be interpreted without turning risk into destiny or an uncertain variant into a diagnosis. Today you practice the professional reasoning behind that work: Most isolated clefts fit a multifactorial threshold model in which many small influences add to risk.
On your WebXam
Distinguishing clean autosomal dominant transmission from the multifactorial threshold model
For life
One result can have many causes; the outcome alone never tells you which.
Principle: Many roads, one ending
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
Several weights tip a balanced scale
A balanced scale can shift after several small weights are added. The final tilt reflects their combined effect, even when no single weight is enough alone.
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
Why might two people carry different combinations?
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 changes when the total crosses the line?
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.
- 1Can one small weight tip the scale by itself?
- 2Why might two people carry different combinations?
- 3What changes when the total crosses the line?
Tier 1 check
Finish with the everyday model
Use the everyday picture to answer today's question in plain words: Can one small weight tip the scale by itself?
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: Add multiple small contributions.
Rule 2: Risk and outcome are not the same thing.
Rule 3: Crossing a threshold can produce a yes-or-no anatomy from graded liability.
Where the analogy stops: Biological liability cannot be measured as literal weights in one person.
Carry the previous idea forward
A syndrome claim requires a repeatable pattern of features, not a cleft plus a familiar gene name.
Today's technical takeaway
Most isolated clefts fit a multifactorial threshold model in which many small influences add to risk.
Now map the same rules onto biology
Model isolated cleft as multifactorial liability
Small weights
Risk alleles and environmental factors
Scale total
Underlying liability
Tip point
Developmental threshold for clefting
Educational illustration, not a clinical photograph or diagnostic result. Use the labeled evidence cards and claim ceiling.
Mateo's case file: evidence supplied in this lesson
GEN03-E1
Mateo's pedigree does not show clean vertical transmission.
Why it matters: A fully penetrant dominant model is a poor fit.
GEN03-E2
Isolated cleft risk is influenced by many genetic loci and non-genetic factors.
Why it matters: Multiple contributors are expected.
GEN03-E3
A person can carry risk factors without developing a cleft.
Why it matters: Penetrance is not all-or-none for each risk factor.
Make the clinical decision
You are selecting the inheritance model for the case board.
The board offers either one dominant allele with complete penetrance or a multifactorial threshold model.
AChoose the multifactorial threshold model.
BChoose complete dominant inheritance despite unaffected parents.
CSay genetics cannot affect isolated clefts.
Choose the model and cite both pedigree and population evidence.
Evidence required
GEN03-E1 + GEN03-E2 Claim ceiling
You may choose the best-fit model. You may not calculate Mateo's exact liability or identify each contributor.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: Genetics lesson 3: Does It Run in Families Like a Single Gene?
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 phenotype is the set of observable features a person has.
- Clefts split into nonsyndromic (no other features, about 70%) and syndromic (packaged with other features, about 30%).
If not, review
Today's new idea is only
How a trait moves through a family tells you whether to expect one gene or many, before you ever find a gene.
Goal: Students will compare clean autosomal dominant inheritance against the multifactorial and use Mateo's sparse, non-vertical pedigree to argue that his fits the multifactorial picture, without yet naming a cause.
Know by the end
- Clean autosomal dominant inheritance needs one altered copy of a single gene and shows : an affected person in almost every generation.
- Multifactorial (threshold) inheritance has no single controlling gene; many small genetic and environmental factors add up to a total liability, and a appears only when liability crosses a threshold.
- About 70% of clefts, the isolated ones, follow the multifactorial model rather than clean dominant .
- Under the multifactorial model, sibling is raised but far below the 50% of a single dominant gene.
1
What clean dominant looks like
Model start: Clean autosomal dominant inheritance needs one altered copy and shows , an affected person in almost every generation.
- A clean autosomal dominant trait sits on a non-sex and needs only ____ altered copy to show.
- Its signature is : an affected person in almost every generation, passed parent to child.
2
Why Mateo does not fit
- Mateo's pedigree shows only Mateo confirmed, his parents ________, and no generation-after-generation pattern.
- That argues against clean dominant .
3
The multifactorial threshold model
- Each person carries a total liability built from many small genetic and environmental risk factors, and a appears only when liability crosses a line.
- This predicts mostly sporadic cases, unaffected parents, and a sibling raised but far below 50%; about 70% of clefts follow it.
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: How a trait moves through a family tells you whether to expect one gene or many, before you ever find a gene.
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 · Genetics domain · Unit 2 How to Screen Your Genes, 2.1 Genetic Testing and Screening
WebXam domain
Molecular and Genetic Technology
Evidence to produce
Write the inheritance line for Mateo's chart stating that the pattern does NOT fit clean autosomal dominant and is best modeled as multifactorial (threshold), and explain in one sentence why a future sibling's recurrence risk would be well below 50%.
Lab / skill
Medical Interventions (MI) · 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.
- Claim: Mateo's fits the ____ model better than clean autosomal dominant.
- Evidence: The pedigree shows ____ confirmed affected person and ____ parents, with no .
- Reasoning: Clean dominant predicts an affected parent and a generational pattern, while the multifactorial predicts ____ cases from many small factors, which is what we see.
How this is graded (rubric)
For: Write the inheritance line for Mateo's chart stating that the pattern does NOT fit clean autosomal dominant and is best modeled as multifactorial (threshold), and explain in one sentence why a future sibling's recurrence risk would be well below 50%.
| 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 inheritance line for Mateo's chart stating that the pattern does NOT fit clean autosomal dominant and is best modeled as multifactorial (threshold), and explain in one sentence why a future sibling's recurrence risk would be well below 50%.".
- 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: Mateo's fits a multifactorial model where many small factors add up. But to understand cleft biology at all, scientists study the best-understood cleft gene in depth. Which gene is the best door into how clefts happen?