Pedigrees. What is a pedigree? A family tree that shows the passage of a trait.
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Transcript of Pedigrees. What is a pedigree? A family tree that shows the passage of a trait.
Pedigrees
What is a pedigree?
• A family tree that shows the passage of a trait
Following Traits in a Pedigree
Steps:
1. Fill in all recessive individuals
2. Determine unknowns
An ExampleThe trait we are tracking is dominant. Determine the genotype of individuals
1, 3, 6, 7
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
DETERMINING MODE OF INHERITANCE ON A PEDIGREE
Modes of Inheritance
• Autosomal Recessive
• Autosomal Dominant
• Sex-linked recessive
• Sex-linked dominant
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
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
For each of the following determine if it can be a recessive trait and/or a
dominant trait
Sometimes____________
A bigger one
1. Is it autosomal recessive or autosomal dominant? How do you know?
2. Write the genotypes of the people you know
Another bigger one
1. Is it autosomal recessive or autosomal dominant? How do you know?
2. Write the genotypes of the people you know
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
FOR EXAMPLE
Another Example
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
Can these pedigrees be recessive sex-linked?
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