Pedigrees

PedigreesPedigreesA tool used to track the inheritance

of traits through a family.

Symbols used by Geneticists

Pedigree SymbolsPedigree Symbols

Male Female

Does not show Trait

Shows Trait

Carrier (heterozygote)

Died from the trait

Reading PedigreesReading Pedigrees

In a pedigree, a circle represents a female; a square represents a male.

Female Male

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Highlighted circles and squares represent individuals showing the trait being studied.

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Circles and squares that are not highlighted designate individuals that do not show the trait.

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A horizontal line connecting a circle and a square indicates that the individuals are parents, and a vertical line connects parents with their offspring.


A half-shaded circle or square represents a carrier, a heterozygous individual.



Each horizontal row of circles and squares in a pedigree designates a generation, with the most recent generation shown at the bottom.

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The generations are identified in sequence by Roman numerals, and each individual is given an Arabic number.

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Queen Victoria, Prince Albert and their 9 Children

Victoria

Edward

AliceAlfred

Helena

LouiseArthurLeopold

Beatrice

Hemophelia Genes

XHXH = Female, normal

XHXh = Female, carrier

XhXh = Female, hemophiliac

XHY = Male, normal

XhY = Male, hemophiliac

Show the cross of…• A woman who is a carrier marries a normal man.

• What is the probability that their children will have the disease? What sex will a child in the family with hemophilia be?

Pedigrees

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