Transcript PEDIGREE CHARTS

What is a pedigree chart?
Pedigree charts show a record of the family
of an individual
 They can be used to study the transmission
of a hereditary condition

© 2007 Paul Billiet ODWS
Symbols used in pedigree
charts
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Normal male
Affected male
Normal female
Affected female
Marriage
A marriage with five children, two
daughters and three sons. The
second son is affected by the
condition.
Eldest child  Youngest child
© 2007 Paul Billiet ODWS
Generations are identified by Roman numerals
Individuals in each generation are identified by Arabic
numerals numbered from the left
Therefore the affected individuals are II3, IV2 and IV3
I
II
III
IV
© 2007 Paul Billiet ODWS
Interpreting a Pedigree Chart
1.
Determine if the pedigree chart shows an
autosomal or X-linked disease.

If most of the males in the pedigree are
affected the disorder is X-linked
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If it is a 50/50 ratio between men and
women the disorder is autosomal.
Example of Pedigree Charts
 Is
it Autosomal or X-linked?
Answer
 Autosomal
Interpreting a Pedigree Chart
2.
Determine whether the disorder is
dominant or recessive.
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If the disorder is dominant, one of the
parents must have the disorder.

If the disorder is recessive, neither
parent has to have the disorder
because they can be heterozygous.
Example of Pedigree Charts
 Dominant
or Recessive?
Answer
 Dominant
Example of Pedigree Charts

Dominant or Recessive?
Answer

Recessive
A Historical Pedigree:

This pedigree is of Egypt’s Ptolemy
dynasty and shows only genealogy,
not traits.
Ptolemy
dynasty
 It
appears almost ladderlike
because of the extensive
inbreeding.
 From 323 B.C. to Cleopatra’s
death in 30 B.C. , the family
experienced
 five brother-sister pairings,
 plus an uncle-niece
relationship.
Cleopatra married her
brother, Ptolemy XIII, when
he was ten years old.
 These type of marriages
were an attempt to preserve
the royal blood.

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