Pedigree
A family tree showing who has a trait. Squares are males and circles are females. Shaded symbols are affected. Pedigrees help work out whether a trait is dominant or recessive and autosomal or X-linked.
Last updated
Analogy
A detective's chart of a family.
In practice
Two unaffected parents with an affected child suggests a recessive trait, with both parents carriers.
Practice
Flashcards
- In a pedigree, what does a circle with a shaded fill mean?An affected female.
Questions people ask
How can you tell if a trait is dominant from a pedigree?
Dominant traits usually appear in every generation, and an affected child has at least one affected parent. Recessive traits can skip generations, and two unaffected parents can have an affected child. If affected fathers have affected daughters but never affected sons by this route, think X-linked.
What does it mean to be a carrier?
A carrier has one copy of a recessive disease allele and one normal allele, so they usually have no symptoms. They can pass the allele on to their children. If both parents are carriers, each child has a 1 in 4 chance of being affected.