Transcript Slide 1

Pedigrees
Pedigrees
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
Pedigrees show how a trait/disorder is passed from
one generation to the next
Symbols:
o
Squares = males (XY), circles = females (XX)
o
Horizontal lines connect breeding couples
o
Vertical lines connect parents to children
o
Shading (filled in) = individual has the trait
o
No shading = individual does not have the trait
o
Half shading or a dot = a carrier
o
A diagonal line means death
o
Roman numerals show generations
o
Numbers assign an individual to a generation
Interpreting Pedigrees
Trait is dominant or recessive?
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Skips a generation = recessive
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Every generation = dominant
Trait is autosomal or sex
linked?
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

Affects ♂ and ♀ equally →
autosomal
Affects ♂ more than ♀ →
sex-linked
Females tend to “carry” a trait
and affect their sons
Females get the trait from
affected father and
carrier/affected mother
Affected males got it from their
mother and give it to their
daughters to “carry.”
aa
Aa
Aa
aa
aa
Aa
Aa
aa
Aa or AA
Aa
aa
aa
Aa
Aa
Autosomal
Autosomal or Sex-linked? ____________________
Dominant
Is this dominant or recessive? ____________________
Assign genotypes to the pedigree to show the inheritance pattern
XBY
XbY
XBXb
XBXb
XBY
XBXb
XbY
XbY
XBXb
XBY
XBXb
XBY
X bY
XBXb
XbY
XbY
Sex-linked
Autosomal or Sex-linked? ____________________
Recessive
Is this dominant or recessive? ____________________
Assign genotypes to the pedigree to show the inheritance pattern
Fill in what you know first!
Pedigree with half-shading to show carriers