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PEDIGREE CHARTS

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PEDIGREE CHARTS A family history of a genetic condition What is a pedigree chart? Pedigree charts show a record of the family of an individual They can be used to ... – PowerPoint PPT presentation

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Title: PEDIGREE CHARTS


1
PEDIGREE CHARTS
  • A family history of a genetic condition

2
What is a pedigree chart?
  • Pedigree charts show a record of the family of an
    individual
  • They can be used to study the transmission of a
    hereditary condition
  • They are particularly useful when there are large
    families and a good family record over several
    generations.

3
Studying human genetics
  • You cannot make humans of different types breed
    together
  • Pedigree charts offer an ethical way of studying
    human genetics
  • Today genetic engineering has new tools to offer
    doctors studying genetic diseases
  • A genetic counsellor will still use pedigree
    charts to help determine the distribution of a
    disease in an affected family

4
Symbols used in pedigree charts
  • Normal male
  • Affected male
  • Normal female
  • Affected female
  • Marriage

5
Organising the pedigree chart
  • A pedigree chart of a family showing 20
    individuals

6
Organising the pedigree chart
  • Generations are identified by Roman numerals

7
Organising the pedigree chart
  • Individuals in each generation are identified by
    Arabic numerals numbered from the left
  • Therefore the affected individuals are II3, IV2
    and IV3

8
Pedigree
Males
Key
Females
Shading
Recessive Trait
No Shading
Dominant Trait
(Free Earlobes F)
I
II
9
What are the Genotypes of the people shown below?
f
f
f
?
?
?
f
f
f
f
10
Interpreting a Pedigree Chart
  • Determine if the pedigree chart shows an
    autosomal or X-linked disease.
  • If most of the males in the pedigree are affected
    the disorder is X-linked
  • If it is a 50/50 ratio between men and women the
    disorder is autosomal.

11
Example of Pedigree Charts
  • Is it Autosomal or X-linked?

12
Interpreting a Pedigree Chart
  • Determine whether the disorder is dominant or
    recessive.
  • If the disorder is dominant, one of the parents
    must have the disorder.
  • If the disorder is recessive, neither parent has
    to have the disorder because they can be
    heterozygous.

13
Example of Pedigree Charts
  • Dominant or Recessive?

14
Example of Pedigree Charts
  • Dominant or Recessive?

15
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16
Summary
  • Pedigrees are family trees that explain your
    genetic history.
  • Pedigrees are used to find out the probability of
    a child having a disorder in a particular family.
  • To begin to interpret a pedigree, determine if
    the disease or condition is autosomal or X-linked
    and dominant or recessive.
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