PEDIGREE SYMBOL

							PEDIGREE SYMBOLS
      AND
     CHARTS
            PEDIGREE
A French term ple de grue or crane’s foot.


DEFINITION: The basic medical pedigree is
 a graphic depiction of how family members
 are biologically and legally related to one
 another from one generation to the next.
 A pedigree is a diagram of family
 relationships that uses symbols to
 represent people and lines to represent
 genetic relationships.
            Uses of Pedigree
• In known mode of inheritance
      -To predict the risk of recurrence.
      -Identifying the at risk individual.
      -Decide on testing strategy.

• Not known inheritance
    -Establish pattern of inheritance.
• Genetic counseling
PEDIGREE SYMBOLS




  INDIVIDUALS
• PROBAND- The member through whom a
  family with genetic disorder is first brought to
  attention of the investigator.
• Also known as index case, propositus(if female),
  proposita(if male).
• CONSULTAND- the person who brings the
  family to attention by consulting a genecist. The
  person may be an affected individual or an
  unaffected relative of a proband.
PEDIGREE SYMBOLS



RELATIONSHIPS
PEDIGREE SYMBOLS



ASSISTED REPRODUCTIVE
     SCENARIOS
  Better to follow

• Draw male partner to the left.
• Each generation should be in the same
  horizontal plane.
• When possible draw siblings in birth order.
• If not possible,record age.
• and individual by Arabic.
    Organising the pedigree chart
      Generations are identified by Roman numerals

       I


       II


      III


      IV
© 2007 Paul Billiet ODWS
    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
                                                       1       2
        I

                                   1       2       3       4   5       6           7
        II

                           1           3       4                               5       6
                               2
      III

                                                                   1       2       3   4   5
      IV
© 2007 Paul Billiet ODWS
• Usually three generations.

• Extend back as far as possible if a health
  problem of significance is identified.
        Common Terminology
• Genome: A set of biological information.
• Genotype: genetic constitution of an
  individual.

• Phenotype: The observable characteristics
  of an individual.
• Dominant: expressed in heterozygote one
  allele present

• Recessive: expressed in homozygote two
  alleles necessary
                   Contd.
• Pleiotropy: A single abnormal gene
  produces diverse phenotypic effects.

• Mutation: Any permanent heritable change
  in the sequence of genomic DNA.

• Exon: A transcribed region of a gene that is
  present in mature messenger RNA.

• Intron: A segment of a gene that is
  transcribed initially but removed from RNA
  transcript.
                     Contd.
• Epigenetic: The factor that can affect the
  phenotype without change in a genotype.

• Gene: a sequence of DNA bases containing
      biologically useful information

• Allele: alternative form of a gene (a mutant?)

• Locus: specific position or location of a gene on
  a chromosome
• Heterogeneity: Similar phenotype determined
  by different genes.
               Contd.

• Penetrance: Frequency of expression of
  genotype.
• Reduced Penetrance: The genotype which
  fails to express.
• Expressivity: The manifestation of
  phenotype differs in people who have
  same genotype .
Pedigree
New Mutation
Quasidominant (A/a X a/a)

       A/a         a/a




 A/a         A/a     a/a       a/a         A/A




                         A/a         A/a         A/a   {A/a
                               A/a
Typical pedigree of AR



           A/a
                   A/a




             A/a         a/A   a/a
     A/A
      Pedigree of XD

I

II

III

IV
      Pedigree of XR disorders

I

II

III

IV
 Always draw
• First degree- parents, siblings, children
• Second degree-Grand parents,, uncles,
  aunts, nephews, nieces and grand
  children.
• Third degree- first cousins ( can just
  mention the number) .
• Fourth degree- first cousins once
  removed