Transcript File - Siegel Science

Pedigrees
•A
pedigree is a diagram of family
relationships that uses symbols to
represent people and lines to
represent genetic relationships.
These diagrams make it easier to
visualize relationships within families.
Basic Information
Circles, squares and lines…
oh my!
More Symbols
1 – Draw a pedigree for a family showing 2 parents & 4 children. Make
the oldest two children boys & the youngest two girls.
Both parents are heterozygous for Brown eyes (B).
2 – Assume the pedigree you drew for #1 is tracing the occurrence of
blue eyes in that family. Show that person II-2 has blue eyes.
3 – Using the pedigree you drew for #1, predict the genotypes of each
person. Remember, blue eyes are recessive to all other colors & follow
the following rules:
1 – Give any person with the trait (those shaded) 2 recessive
alleles.
2 – Give everyone else (those not shaded) 1 dominant allele.
3 – Determine the genotype for each person using your
knowledge of heredity.
More Interpretation
Determining if the pedigree shows
autosomal or X-linked disease.
1. If most of the males in the pedigree
are affected, the disorder is X-linked
(sex linked)
2. If it is a 50/50 ratio between men and
women, the disorder is autosomal.
Autosomal or X-linked?
Autosomal – Why?
Even More Interpretation….
Determine whether the disease is
dominant or recessive.
1. If the disorder is dominant, one of the
parents must have the disorder.
2. If the disorder is recessive, neither of
the parents has to have the disorder
because they can be heterozygous.
3. Recessive disorders can skip
generations.
•
Dominant or Recessive?
Dominant – Why?