pedigrees. what is a pedigree? a family tree that shows the passage of a trait
TRANSCRIPT
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Pedigrees
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What is a pedigree?
• A family tree that shows the passage of a trait
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Following Traits in a Pedigree
Steps:
1. Fill in all recessive individuals
2. Determine unknowns
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An ExampleThe trait we are tracking is dominant. Determine the genotype of individuals
1, 3, 6, 7
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This pedigree is for lung disease. The trait is recessiveWhat is the genotype for individuals
2, 4, 10, 12 and 13
1 2
987
65
43
1312
1110
14 15 16
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DETERMINING MODE OF INHERITANCE ON A PEDIGREE
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Modes of Inheritance
• Autosomal Recessive
• Autosomal Dominant
• Sex-linked recessive
• Sex-linked dominant
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Autosomal Dominant vs. Recessive
• Things to look for– Autosomal Recessive traits
• Occur less often• Skip generations• Two parents with the trait MUST give the trait to
their kids
– Autosomal Dominant Traits• Occurs more often
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How can we figure it out
• Look for sections of the family that the parents either both – have the trait – do not have traitFirst assume the trait dominant (assume all
dominant people are heterozygous) and see if it possible
Then assume it is recessive (assume all dominant people are heterozygous) and see if it possible
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For each of the following determine if it can be a recessive trait and/or a
dominant trait
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Sometimes____________
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A bigger one
1. Is it autosomal recessive or autosomal dominant? How do you know?
2. Write the genotypes of the people you know
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Another bigger one
1. Is it autosomal recessive or autosomal dominant? How do you know?
2. Write the genotypes of the people you know
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What if you cannot find parents that either don’t have it or do have it.
Cry!
Traits that occur less often are usually recessive
Traits that skip generations are usually recessive
To be sure you have to go through the entire pedigree and assume each possibility
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FOR EXAMPLE
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Another Example
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Recessive Sex-Linked
• More men will be affected
• an affected female will transmit the trait to all male children
• In order to have an affected female the dad must have the trait
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Can these pedigrees be recessive sex-linked?
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Other Types of Inheritance
• Sex-linked dominant• If Dad has the trait, all the daughters must have the
trait
• Y linked:• If Dad has the trait, all the sons must have the trait
• Mitochondrian Genes• An affected mother will give the trait to all children