Pedigree logic
Wed, Oct 21, 2026 · Week 9 · Genetics of Disease (Medical Interventions)
Today's goal: Use pedigree symbols to track an inherited trait and identify carriers across generations.
What a finished product looks like
This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.
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 |
Also due today: Submit your pedigree and inheritance call to the course shell.
WebXam problem for today's skill
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.