2. Pedigree charts
Why do we use them?
Because experimental crosses with humans are not
possible.
Then what information do we use to determine
inheritance of traits?
-Medical history
-Historical data
-Family records
3. Pedigree charts
Some symbols to remember:
Normal female Female with phenotype of interest
Normal male Male with phenotype of interest
Normal (sex is unknown) Person with phenotype of interest
(unknown sex)
Female heterozygous for recessive allele
Male heterozygous for recessive allele
5. Pedigree charts
Some symbols to remember:
I
II
One-egg Two-egg
Monozygotic dizygotic
Identical twins fraternal twins
6. Pedigree charts
How do we use a pedigree chart?
When people have children…
Mother’s family Father’s family
I
II
III
If this child had a
genetic disease, we can
trace who it came from
by completing the
pedigree from family
and medical records
15. Pedigree charts
Autosomal recessive:
Involves a recessive allele on
a non-sex chromosome
Autosomal dominant:
Involves a dominant allele
on a non-sex chromosome
X-linked recessive:
Involves a recessive allele on
the X-chromosome
X-linked dominant:
Involves a dominant allele
on the X-chromosome
Y-linked: Involves an allele
on the Y-chromosome
