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Pedigrees
Suppose you wanted to learn about an inherited
trait present in your family. One method could be
using a pedigree.
• A pedigree is a chart of symbols showing the
relationships within a family & a specific trait that
each member may exhibit.
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Pedigree Symbols
2
Connecting Pedigree Symbols
Examples of connected symbols:
• Married Couple
• Siblings
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• What does a pedigree chart look like?
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Interpreting a Pedigree Chart
Determine whether the disorder is dominant or
recessive.
– 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.
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Example of Pedigree Charts
• Dominant or Recessive?
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Example of Pedigree Charts
• Dominant or Recessive?
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Mr. and Mrs. Smith had 3 children – Susie,
Sandra, & Steven. When the children were
still young, Mr. Smith was killed in an
automobile accident. Three years after the
accident, Mrs. Smith married Mr. Jones.
Mr. Jones had 1 daughter, Joy. Mr. Jones &
Joy’s mother had been divorced when Joy
was 6.
Draw a pedigree for each of the following
families:
1. The Smith family before the automobile
accident.
2. The Smith-Jones family after the new
marriage.
Interpreting a Pedigree Chart
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
– If it is a 50/50 ratio between men and
women the disorder is autosomal.
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Example of Pedigree Charts
• Is it Autosomal or X-linked?
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Summary
• Pedigrees are family trees that explain your
genetic history.
• Pedigrees are used to find out the
probability of a child having a disorder in a
particular family.
• To begin to interpret a pedigree, determine
if the disease or condition is autosomal or
X-linked and dominant or recessive.
11
Female Carriers
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Mr. and Mrs. Smith had 3 children – Susie,
Sandra, & Steven. When the children were
still young, Mr. Smith was killed in an
automobile accident. Three years after the
accident, Mrs. Smith married Mr. Jones. Mr.
Jones had 1 daughter, Joy. Mr. Jones &
Joy’s mother had been divorced when Joy
was 6.
Draw a pedigree for each of the following
families:
1. The Smith family before the automobile
accident.
2. The Smith-Jones family after the new
marriage.
Imagine you are a genetic counselor. The
pedigree shown illustrates albinism. A couple
from the family have come to you for advise
about how the trait is inherited. Your task is
to determine whether the allele for albinism
is dominant or recessive.
•
Choose an inherited trait & create a pedigree
Some doctors include pedigrees in patients’
medical charts. List at least 3 types of things word problem that will be drawn by a fellow
that a doctor might include in a pedigree that biology student. Include 4 generations.
most people would probably not include in a
family tree.
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