Pedigrees
Family trees trace how traits pass down generations.
About this topic
A pedigree is a family tree charting the inheritance of a trait through generations. Squares are males, circles females, shaded symbols show the trait, and horizontal lines connect partners. By analysing patterns, you can deduce whether a trait is dominant or recessive and autosomal or sex-linked.
If two unaffected parents have an affected child, the trait is recessive. If every affected person has an affected parent, it's likely dominant. Genetic counsellors use pedigrees to assess risks.
When two unaffected parents have an affected child, the trait must be recessive, since the parents were hidden carriers. If an affected person appears in every generation and has an affected parent, the trait is likely dominant. If more males than females are affected and the trait skips generations passing through mothers, suspect X-linked recessive.
Doctors and genetic counsellors use pedigrees to calculate risk for couples planning children. Practise by labelling each person's likely genotype, starting with those you are certain about, such as affected individuals with a recessive trait, who must be homozygous. A common mistake is assuming that a trait appearing in only one branch must be rare in the population or must be dominant. Careful reasoning from the pattern is the key.
Key ideas
- Squares male, circles female
- Shaded means affected
- Infer inheritance patterns
Quick check
Use cases: where Pedigrees helps
- Homework: review the key idea behind Pedigrees before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Pedigrees without notes.
- Visual learning: play with the interactive lab to see how Pedigrees changes when you adjust its inputs.
- Teaching a friend: explain Pedigrees in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Pedigrees?
Family trees trace how traits pass down generations.
What will I learn in Pedigrees?
Squares male, circles female. Shaded means affected. Infer inheritance patterns.
Is Pedigrees part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Pedigrees lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Pedigrees?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.