Pedigree Analysis

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Pedigree Analysis
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Pedigrees

• Pedigrees are like genetic family trees

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Basic Symbols
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More Symbols
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Draw the pedigree below in the space given on
your paper. We will complete it together.
1
2
Aunaffected (unshaded) aaffected (shaded)
I.
Aa
Aa
6
5
4
3
1
2
II.
Aa
Aa
A_
A_
aa
A_
4
3
2
1
6
5
III.
aa
Aa
Aa
A_
A_
A_
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Dominant vs. Recessive

• Is it a dominant pedigree or a recessive
  pedigree?
• 1. If two affected people have an unaffected
  child, it must be a dominant pedigree D is the
  dominant mutant allele and d is the recessive
  wild type allele. Both parents are Dd and the
  normal child is dd.
• 2. If two unaffected people have an affected
  child, it is a recessive pedigree R is the
  dominant wild type allele and r is the recessive
  mutant allele. Both parents are Rr and the
  affected child is rr.
• 3. If every affected person has an affected
  parent it is a dominant pedigree.

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Sample Pedigree 1
1
2
Aaffected (shaded) aunaffected (unshaded)
I.
Aa
Aa
1
5
4
3
6
2
7
II.
A_
aa
aa
Aa
Aa
A_
aa
6
4
1
8
7
5
3
2
III.
aa
aa
aa
aa
Aa
Aa
Aa
A_
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Questions

1. Which trait is dominant, the affected or normal
   individual?
2. What is the genotype of II-3?
3. What is the genotype of II-7?
4. (T or F) The genotype of II-1 and II-2 are the
   same.
5. (T or F) The original parents are homozygous for
   the trait.
6. (T or F) If II-5 had children they could be
   affected.

Affected
Aa
A_
True
False
True
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Sample Pedigree 2
1
2
Aunaffected (unshaded) aaffected (shaded)
I.
Aa
Aa
5
4
3
1
6
2
7
II.
Aa
aa
Aa
aa
Aa
A_
aa
6
4
1
8
7
5
3
2
III.
aa
aa
Aa
Aa
A_
aa
A_
aa
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Questions

1. Is the affected trait dominant or recessive?
2. What is the genotype of III-6 and III-8?

Recessive
A_
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