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Pedigree Analysis

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Pedigree Analysis Have you ever seen a family tree do you have one?? Graphic representation of family inheritance. Pedigree of Queen Victoria – PowerPoint PPT presentation

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Title: Pedigree Analysis


1
Pedigree Analysis
Have you ever seen a family tree do you have
one?? Graphic representation of family
inheritance.
2
What is a pedigree?
  • Shows a pattern of inheritance in a family for a
    specific trait (phenotype)
  • Genotypes can usually be determined
  • Why would we want to use a pedigree in genetics?
  • To track the occurrence of diseases such as
  • Cystic fibrosis 1/2500 mucus accumulates
    (white North Amer.)
  • Tay-Sachs disease lipids accumulate in CNS
    (Jewish)
  • Phenylketonuria missing enzyme causes problems
    in CNS (Nordic/Swedish)

3
The Symbols used
Roman Numerals indicate generations
Children of a generation are in order from left
to right and numbered
4
Sample pedigree
How many females show the trait being
studied? What is the sex of offspring III-9? How
many offspring did the generation I parents
have? What is the difference between the II-3 4
and IV-2 3?
5
Inheritance patterns
  • Autosomal dominant
  • The disease can be passed from the father to the
    son , this never happens with X-linked traits.
  • The disease can occur in three consecutive
    generations, this never happens with recessive
    traits.
  • Males and females are affected, with roughly the
    same probability.
  • Example Polydactyly

6
Inheritance patterns
  • Autosomal recessive
  • Males and females are equally likely to be
    affected.
  • The trait is usually found in siblings, not
    parents of affected or the offspring of affected.
  • Is more common than the general population when
    consanguinous mating occurs
  • (think inbreeding of dogs)
  • Cystic fibrosis
  • Tay-Sachs disease

7
Inheritance patterns
  • Sex-linked recessive conditions
  • The disease is never passed from father to son.
  • Males are much more likely to be affected than
    females.
  • All affected males in a family receive the trait
    through their mothers.
  • Examples
  • Colour-blindness
  • Duchenne Muscular Dystrophy
  • Hemophila
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