Pedigree logic
Open your materials, follow the steps, then turn in your work.
Use pedigree symbols to track an inherited trait and identify carriers across generations.
1. Open your materials
Use the materials named in the first step below. Open lesson resources.
2. Start the work
Draw the standard pedigree symbols: square, circle, and a line for a mating, and label affected versus unaffected.
Show all 5 required steps
- Draw the standard pedigree symbols: square, circle, and a line for a mating, and label affected versus unaffected.
- Map the family in the shell dataset across three generations using those symbols.
- Decide whether the trait is dominant or recessive and write one line of evidence from the pattern.
- Circle every individual who must be a carrier and explain one of them.
- Submit your pedigree and inheritance call as your daily evidence.
Lost your place? Lost your place? If your symbol key (square, circle, mating line, affected vs. unaffected) is not drawn yet, start there (step 1). If your three-generation map is already drawn, move to circling every forced carrier and explaining one (step 4), then submit.
Check your work before submitting
- You'll be able to build a correct three-generation pedigree.
- You'll be able to identify carriers and the mode of inheritance from the pattern.
Before lab work: read the safety rules
- Wear the required PPE, keep the bench clear, handle equipment only as directed, and know where the eyewash, sink, and spill kit are before you start.
- Human samples and data stay private: label with a code, never a name, and dispose of materials in the correct waste container, then wash your hands.
3. Turn in your work
DueCheck Schoology- Hand in
- Completed three-generation pedigree with carriers circled, mode of inheritance stated, and one sentence of evidence.
How to submit and name your file
Use the submission route shown on today's today's page.
In Schoology, open your course and the assignment for this lesson. Attach your file, select Submit, and check that it appears in the submission.
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How this lesson connects
Keep using what you learned last class: Should terminally ill patients be offered medical aid in dying in order to decrease antibiotic use? Today: Two unaffected parents can each carry a silent recessive allele, so an affected child appearing from healthy parents is strong evidence the trait is recessive, not a break in the family tree.
Optional: listen or watch a unit review▸
Need help? Warm-up, timing, and directions▸
💡 Big idea: Two unaffected parents can each carry a silent recessive , so an affected child appearing from healthy parents is strong evidence the trait is recessive, not a break in the family tree.
- 0-8Teach pedigree symbol conventions; practice drawing one mating pair
- 8-25Map the case family from dataset across three generations
- 25-40Determine dominant vs. recessive from pattern; write evidence sentence
- 40-55Circle all obligate carriers; write one-sentence explanation for one
- 55-70Partner check: verify each other's pedigrees for symbol errors
- 70-80Submit pedigree and inheritance call to the class site
- • Hook: Show a three-generation family photo and ask: can you tell from a photo who carries a hidden gene?
- • Why it matters: Genetic counselors read pedigrees to estimate the risk a client's future children will be affected.
- • Today's work: You will build and read a pedigree to make exactly that kind of call.
- • Exit goal: Completed three-generation pedigree with carriers circled and inheritance mode stated.
- • Pedigree conventions: squares are male, circles are female, filled shapes are affected, a line connects mates.
- • If two unaffected parents produce an affected child, the trait is autosomal recessive.
- • A has one working and one non-working ; they do not show the trait but can pass it on.
PLTW connection and today's work
Open Activity 2.1.1 Chronicles of a Genetic Counselor in myPLTW and use the case family dataset to build your three-generation pedigree.
Today's stopping point: Monday debate should be posted; pedigree due today.
PLTW activity titles identify the course connection. If your account will not open, use the posted materials for today and tell Mr. Mendoza. Do not mark an online activity complete unless you completed it.
Course connection
- Activity 2.1.1 Chronicles of a Genetic Counselor
Use the turn-in directions at the top of this page. Do not create a second submission unless your teacher asks for one.
Show another explanation or a smaller first step
Need help? Choose a starting point
Finish the assigned lab safely before starting extra practice.
Lesson resources: reading, slides, and vocabulary▸
The deck carries the prior idea forward, lets you inspect an analogy, maps the rule to biology, and ends with the same evidence decision and exit ticket used on this page.
Generated from this lesson's canonical data with a red-team citation check.
Should terminally ill patients be offered medical aid in dying in order to decrease use?
Two unaffected parents can each carry a silent recessive , so an affected child appearing from healthy parents is strong evidence the trait is recessive, not a break in the family tree.
A family evidence board traces possible combinations through each generation while keeping probability separate from certainty.
- Which inheritance pattern fits the supplied relationships?
- Which genotypes remain possible?
- Does the probability describe one possible outcome or guarantee it?
Trace possibilities generation by generation, test the inheritance pattern against every supplied relationship, and report risk as a probability rather than a prediction of one person's outcome.
A simplified pedigree can omit penetrance, de novo changes, uncertain relationships, environmental effects, and other information needed for real .
- • Family symbols map to the supplied phenotype record.
- • branches map to possible transmissions.
- • The final fraction maps to a conditional probability, not a guaranteed outcome.
Driving question: In this three-generation family, two parents who show no sign of the condition have a child who is affected. What does that single fact force you to conclude about how the trait is inherited?
What you already know: Should terminally ill patients be offered medical aid in dying in order to decrease use?
New idea: Two unaffected parents can each carry a silent recessive , so an affected child appearing from healthy parents is strong evidence the trait is recessive, not a break in the family tree.
Visual or model: F1. F1. A lesson illustration or teaching diagram for Pedigree logic. Use it with E1-E3; it is a model or context image, not experimental or patient data. What to notice: Trace the labeled testing, treatment, or biological process and identify where evidence limits the decision.
- Observe or measure the relevant feature in pedigree logic.
- Organize the observation with a stable evidence ID.
- Apply this rule: Trace possibilities generation by generation, test the inheritance pattern against every supplied relationship, and report risk as a probability rather than a prediction of one person's outcome.
- Choose the option the evidence supports and state the limit of the conclusion.
Real biomedical example: In this three-generation family, two parents who show no sign of the condition have a child who is affected. What does that single fact force you to conclude about how the trait is inherited?
What the evidence supports: E1-E3 and F1 support the daily take-home when the response meets the stated success criteria.
What it cannot prove: The package does not support claims beyond this lesson's or any real patient diagnosis.
- • : One of the alternative versions of a gene found at the same spot on a , like the A, B, and O versions of the blood-group gene.
- • : The specific set of gene versions an individual carries, which works with the environment to shape observable traits.
- • phenotype: The observable traits of an organism, such as appearance or function, that result from its combined with environmental influences.
- • pedigree: A family tree drawn with standard symbols (squares for males, circles for females, filled for affected) so any geneticist can read a family at a glance.
- • SNP: A single-nucleotide polymorphism, a one-letter difference in DNA at a specific spot that varies between people.
- • : A person who carries one copy of a disease without showing symptoms but can pass it to their children.
- • : A guided conversation with a trained specialist who explains inherited disease risks, test options, and choices to help a family make informed decisions.
Use it now: Choose one decision option. Cite E1 and E3, then explain how the rule connects the evidence to your choice.
Go further, optional: The source links below are optional enrichment. Every fact required for today's local evidence decision appears in this lesson package.
Genetic evidence can support an inheritance, , sequence, or expression explanation, but penetrance, regulation, environment, family structure, and test uncertainty can limit the conclusion.
Limit: A classroom , , pedigree, or molecular model does not establish a real person's diagnosis, prognosis, identity, or reproductive outcome.
Trace possibilities generation by generation, test the inheritance pattern against every supplied relationship, and report risk as a probability rather than a prediction of one person's outcome.
Limit: A simplified pedigree can omit penetrance, de novo changes, uncertain relationships, environmental effects, and other information needed for real .
You can build a correct three-generation pedigree.
Limit: E3 defines the classroom product or success criterion. It is not independent scientific evidence and cannot justify a clinical or causal claim.
PLTW-GEND-2026-10-16 · Simulated classroom evidence scenario
Your role: medical interventions team member
Decision: Your team must decide what the evidence from pedigree logic supports before submitting the labeled and result claim named on today's page.
- • Conclude that non-tasters are missing the taste gene, since a difference you can feel needs a big DNA change.
- • Collect matching and taste results from a second, separate group before treating one letter as the whole story.
- • Explain the tasting difference as one swapped base in TAS2R38 that alters the bitter taste .
Response: State one choice, cite at least two evidence IDs, explain the rule that connects them, and add one limitation. Submit it as the labeled and result claim.
Claim ceiling: Today's evidence supports a classroom claim about pedigree logic. It cannot prove causation, diagnose a real patient, or justify action outside this room.
Reason for review: Your team must decide what the evidence from pedigree logic supports before submitting the labeled and result claim named on today's page.
Context: A pedigree turns a family's story into a testable pattern, because the way a trait appears and skips across generations is enough to tell you whether an is dominant or recessive without ever running a DNA test.
- • T1: Draw the standard pedigree symbols: square, circle, and a line for a mating, and label affected versus unaffected.
- • T2: Map the family in the shell dataset across three generations using those symbols.
- • T3: Decide whether the trait is dominant or recessive and write one line of evidence from the pattern.
- • T4: Circle every individual who must be a and explain one of them.
- • T5: Submit your pedigree and inheritance call as your daily evidence.
- • E1: Genetic evidence can support an inheritance, , sequence, or expression explanation, but penetrance, regulation, environment, family structure, and test uncertainty can limit the conclusion.
- • E2: Trace possibilities generation by generation, test the inheritance pattern against every supplied relationship, and report risk as a probability rather than a prediction of one person's outcome.
- • E3: You can build a correct three-generation pedigree.
Measurements: Use only the measurements, units, graph, or counts supplied in today's task. No additional patient measurement is implied.
Figure finding: Teaching diagram for Pedigree logic. Trace the labeled testing, treatment, or biological process and identify where evidence limits the decision. This is a teaching model, not patient or experimental data.
Uncertainty: This is a composite classroom scenario. Missing history, measurements, or confirmation tests remain unknown and limit the conclusion.
Mean = sum of values / number of values. Median = middle ordered value. Range = maximum - minimum.
For 2, 4, 4, and 10: mean = 20 / 4 = 5, median = 4, and range = 10 - 2 = 8.
Mean, median, and range keep the measurement unit. Order the values before finding the median.
Calculate the requested summary for today's supplied values, then write what it reveals and what it hides.
Students often think Students think that if a child shows a trait, at least one parent must also show that trait, because they picture traits as always visible when present.. The trap: Two unaffected parents can carry one hidden recessive each and pass both to a child. The trait was there the whole time, just silent. Assuming an affected child needs an affected parent will make you call recessive patterns 'dominant' and misread the whole pedigree.
I drew the family using standard symbols: squares for males, circles for females, filled-in shapes for affected individuals, and a horizontal line for each mating.
Mode of inheritance: This trait is autosomal recessive.
Evidence from the pattern: In Generation II, two unaffected parents produced an affected daughter. Two unaffected parents can only have an affected child if both are carriers of a recessive allele, so the trait must be recessive (not dominant), and it appears in both sexes, so it is autosomal, not X-linked.
Carriers I circled: Both Generation II parents must be carriers, because each had to pass one recessive allele to their affected child while showing no trait themselves. I circled both. I can explain the father: he is unaffected, so he has at least one working allele, but his affected child received a non-working allele from him, so he must carry one of each.
| Individual | Symbol | Status |
|---|---|---|
| Gen I male | square | unaffected |
| Gen II father | square | carrier (circled) |
| Gen II mother | circle | carrier (circled) |
| Gen III daughter | filled circle | affected |
This model shows the level of evidence and organization needed to complete: Completes the pedigree analysis: a correctly drawn three-generation pedigree with carriers circled, the mode of inheritance stated, and one sentence of evidence from the pattern.
- Name the variables and include units.
- Enter observations without changing the raw values.
- Check labels, calculations, and patterns before interpreting the data.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Submit your pedigree and inheritance call to Schoology.
- CER:
- Claim, Evidence, Reasoning: make a claim, back it with evidence, explain your reasoning.
- SOP:
- Standard Operating Procedure, the exact steps to follow (especially in a lab).
- Tracker:
- Your PLTW progress log where you record completed evidence.
- myPLTW:
- The PLTW course site where you do the online activities. Find it in Clever with your Microsoft sign-in, right next to Schoology.
Tap the speaker to hear a term. Add two of these to your notebook glossary with a definition and an example in your own words.
Pick just 2 or 3 words from today and make them yours: write what each one means in your own words, name the context clue or evidence that helped, then give one example from what you actually did in Pedigree logic. Try your own words first; the glossary is there if you get stuck. This is voluntary and counts as extra credit, so keep it short.
Saved on this device. Show Mr. Mendoza or add these to your notebook glossary to claim the extra credit.
Play the cold open at the start of the unit to set the scene. Each recording is AI-generated and simulated (fictional callers, no real people or student data).
Classroom documents for this lesson are posted in Schoology. Open Clever, then Schoology, and find each one by the name shown on its card.
Use this after the required lesson work when you are ready for a harder application or a deeper connection.
Placement rationale
Matched Genetic testing, PTC, pedigree, SNPs by path:Medical-Interventions/Unit-2_How-to-Screen-Your-Genes/2.1_Genetic-Testing-and-Screening; keywords:genetic testing, screening, ptc. Score 150. Visibility: student-schoology (student-facing resource; link through Schoology rather than local path).
Use this as the classroom resource for Genetic testing, PTC, pedigree, SNPs.
Placement rationale
Matched Genetic testing, PTC, pedigree, SNPs by path:Medical-Interventions/Unit-2_How-to-Screen-Your-Genes/2.1_Genetic-Testing-and-Screening; keywords:genetic testing, screening, snp. Score 146. Visibility: student-schoology (student-facing resource; link through Schoology rather than local path).
Use this if you were absent, got stuck, or need another pass before you submit the lesson artifact.
Placement rationale
Matched Genetic testing, PTC, pedigree, SNPs by path:Medical-Interventions/Unit-2_How-to-Screen-Your-Genes/2.1_Genetic-Testing-and-Screening; keywords:genetic testing, screening. Score 142. Visibility: student-schoology (student-facing resource; link through Schoology rather than local path).
Sign in to Clever with your district Microsoft account to open Schoology or myPLTW. Follow today's posted steps. If myPLTW will not open, use the posted alternative and tell Mr. Mendoza. Turn in your completed work through the Schoology assignment.
Practice: try a question, then check your answer▸
Claim ceiling for this check: Today's evidence supports a classroom claim about pedigree logic. It cannot prove causation, diagnose a real patient, or justify action outside this room.
In a pedigree, an unaffected mother and an unaffected father have a daughter who is affected. Is the trait dominant or recessive, and what must be true about each parent's genotype?
Write an answer and pick a confidence to unlock the key.
Fast retrieval with instant answers, not the commit-then-reveal check above. Try each from memory first: write what you remember about the earlier units, then check yourself here.
Missed class or ready for more?▸
Run this before you touch the bench. It is built from the real lab procedure, so the decisions you make here are the ones you will make with the equipment in your hands.
Wednesday's SNP case uses the same family pedigree you built today. Before then, review what a single-nucleotide polymorphism is: a one-letter change in the DNA sequence that can determine genotype. Make sure your pedigree is saved and accessible.
Finish the checklist before you handle any material.
- • Wear the required PPE, keep the bench clear, handle equipment only as directed, and know where the eyewash, sink, and spill kit are before you start.
- • Human samples and data stay private: label with a code, never a name, and dispose of materials in the correct waste container, then wash your hands.
- 1Before materials are handled, identify the purpose, variables or comparison, controls, measurement units, and stop-work condition.
- 2Draw the standard pedigree symbols: square, circle, and a line for a mating, and label affected versus unaffected.
- 3Map the family in the shell dataset across three generations using those symbols.
- 4Decide whether the trait is dominant or recessive and write one line of evidence from the pattern.
- 5Circle every individual who must be a carrier and explain one of them.
- 6Submit your pedigree and inheritance call as your daily evidence.
- 7Record each result in the prepared table before interpreting it. Mark missing, repeated, or invalid results truthfully.
- 8Complete the named cleanup and waste route, remove PPE safely, wash hands when required, and confirm the station is ready for the next group.
| Trial or sample ID | Independent condition | Measured result with units | Observation before interpretation | Quality-control note |
|---|---|---|---|---|
Before the procedure, predict the result and cite the rule behind the prediction.
After the procedure, compare the result with the prediction and name one limitation or source of uncertainty.
What today's skills lead to. These are real health-science careers this course builds toward. Tap one to see, on the US Department of Labor's O*NET site, what the job actually involves, what it pays, and how fast it is growing.
Today is individual work you can do from home: complete the same target above, then submit your Data table.
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. If you cannot get in, see Mr. Mendoza. Do not skip the work.
Class still runs. Complete the online activity above (it's self-guided). Need the concept taught without a teacher? Use this authoritative explainer:
MedlinePlus: What is genetic testing?- CompleteEvery required part of the artifact is present, nothing left blank.
- AccurateThe science and the data are correct and match the evidence.
- Scientific reasoningYou explain your claim with evidence and reasoning (CER), not just an answer.
- Professional communicationClear, organized, labeled, and written the way a clinician or scientist would.
- SubmittedGo 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. If you cannot get in, see Mr. Mendoza. Do not skip the work.
- Error analysis and method · counts doubleName a specific limit of the method and how it moved your result, and compare what you predicted to what happened. "Human error" does not count; say what about the procedure or instrument caused it.
This week
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