Pedigree ChartsPedigree Charts

The family tree of geneticsThe family tree of genetics

OverviewOverview

I.I. What is a pedigree?What is a pedigree?a.a. Definition Definition

b.b. Uses Uses

II.II. Constructing a pedigree Constructing a pedigreea.a. Symbols Symbols

b.b. Connecting the symbols Connecting the symbols

III.III. Interpreting a pedigree Interpreting a pedigree

What is a Pedigree?What is a Pedigree?

♣♣A pedigree is a chart of the genetic historyA pedigree is a chart of the genetic historyof family over several generations.of family over several generations.

♣♣Scientists or a genetic counselor would findScientists or a genetic counselor would findout about your family history and make thisout about your family history and make thischart to analyze.chart to analyze.

Constructing a PedigreeConstructing a Pedigree

♣♣MaleMale

♣♣FemaleFemale

Connecting Pedigree SymbolsConnecting Pedigree Symbols

♣♣Fraternal twinsFraternal twins

♣♣Identical twinsIdentical twins

Examples of connected symbols:Examples of connected symbols:

Connecting Pedigree SymbolsConnecting Pedigree Symbols

♣♣Married CoupleMarried Couple

♣♣SiblingsSiblings

Examples of connected symbols:Examples of connected symbols:

ExampleExample

♣♣What does a pedigree chart look like?What does a pedigree chart look like?

Symbols in a Pedigree ChartSymbols in a Pedigree Chart

♣♣AffectedAffected

♣♣X-linked (color half in)X-linked (color half in)

♣♣Autosomal carrierAutosomal carrier

♣♣DeceasedDeceased

Interpreting a Pedigree ChartInterpreting a Pedigree Chart

1.1. Determine if the pedigree chart shows anDetermine if the pedigree chart shows anautosomal or X-linked disease.autosomal or X-linked disease.

–– If most of the males in the pedigree areIf most of the males in the pedigree areaffected the disorder is X-linkedaffected the disorder is X-linked

–– If it is a 50/50 ratio between men andIf it is a 50/50 ratio between men andwomen the disorder is autosomal.women the disorder is autosomal.

Example of Pedigree ChartsExample of Pedigree Charts

♣♣ Is it Autosomal or X-linked?Is it Autosomal or X-linked?

AnswerAnswer

♣♣AutosomalAutosomal

Interpreting a Pedigree ChartInterpreting a Pedigree Chart

2.2. Determine whether the disorder isDetermine whether the disorder isdominant or recessive.dominant or recessive.

–– If the disorder is dominant, one of theIf the disorder is dominant, one of theparents must have the disorder.parents must have the disorder.

–– If the disorder is recessive, neitherIf the disorder is recessive, neitherparent has to have the disorder becauseparent has to have the disorder becausethey can be heterozygous.they can be heterozygous.

Example of Pedigree ChartsExample of Pedigree Charts

♣♣Dominant or Recessive?Dominant or Recessive?

AnswerAnswer

♣♣DominantDominant

Example of Pedigree ChartsExample of Pedigree Charts

♣♣Dominant or Recessive?Dominant or Recessive?

AnswerAnswer

♣♣RecessiveRecessive

SummarySummary

♣♣Pedigrees are family trees that explain yourPedigrees are family trees that explain yourgenetic history.genetic history.

♣♣Pedigrees are used to find out thePedigrees are used to find out theprobability of a child having a disorder in aprobability of a child having a disorder in aparticular family.particular family.

♣♣To begin to interpret a pedigree, determineTo begin to interpret a pedigree, determineif the disease or condition is autosomal or X-if the disease or condition is autosomal or X-linked and dominant or recessive.linked and dominant or recessive.